It seems like netlisting is a four letter word amongst a lot of gamers, often used as a derogatory term for an army list that appears to be copied from the internet. Netlists are also often assumed to be high-powered lists, and that by using them you are somehow cheating or playing with an unfair advantage.
This CONCEPTS: article seeks to establish a clear understanding of the definition, pros and cons of netlisting.
For the purposes of this discussion, I will define a netlist as an army list that is commonly found on the internet, whether it be on forums, blogs or wherever, including minor variations on it's build-up. I will not include any and all lists that are on the web, uncommon or unique lists, otherwise every list on the web would be a netlist!
Personally, I can understand how satisfying it can be to create and play (and win!) with your own unique list. The army is your own and can be an extension of your personality and preferences, both visually and strategically. However, when playing competitively, I think that this attitude can be restrictive.
As I have briefly said before, a netlist can be a very useful tool for players looking to learn an army or particular playstyle. Also, choosing a list that consistently does well across a number of different tournaments means that any purchases are much more likely to be useful, hopefully avoiding dud units or models. This is a massive put-off for new players, having spent however much money and time getting their army ready to play, only to find out that half (or more!) of it is commonly thought of as terrible.
Using a netlist can give you the confidence that your army has the capacity to win games. I have heard so many players blaming their army or their dice for their losses, but I've never seen anyone with continually bad luck and when you're using a proven list, I'd humbly suggest that repeated losses are down to the general! At least with a decent netlist you can identify where the weakness is and work on improving your gameplay, rather than keep swapping around units or blaming the dice. It's also possible to read battle reports to see how others are using the list against different opponents to pick up strategies and tactics you might otherwise have missed.
As useful as it can be to learn the ropes using a netlist, there are plenty of pit-falls and disadvantages.
Choosing the right list
Although it seems like an easy thing to do to just go on the net and pick up a list, there are lots of bad ones around! When you're still getting to grips with a game, the problem is you might not know how to differentiate the good from the bad. Not only this, the lists you find may not be accurate. Sometimes lists are typed up by opponents who remember certain things incorrectly, so I strongly suggest verifying the list's authenticity before spending any money copying it!
To further complicate matters, there are some lists that are specifically build for certain tournaments and their variation of the rules. For example, if you were to take a list from NOVA, commonly accepted as one of the most competitive tournaments around, without doing some research you may not realise that the terrain set-up always includes a large line of sight blocking piece in the centre (greatly assisting assault oriented armies), that the missions are tiered into primary, secondary and tertiary objectives or that vehicles can never be scoring (e.g. in The Scouring).
Looking at the lists that did well in this environment, it was clear that many of the armies were built specifically to take advantage of, or at least avoid the disadvantages, of the tournament specific ruleset. This means that the performance of a list from that year's NOVA playing basic rule book missions with normal terrain is likely to be very different (and presumably worse).
Another example is the ETC (or equivalents). These team tournaments allow captains to pick their match-ups, so it is possible for a list to be designed in such a way as to be very strong against certain enemies, with the intention of tying to avoid it's bad match-ups. Copying a list that appeared to do very well doesn't mean that it would necessarily do so in a standard tournament setting.
Added to this, a large number of tournament players 'metagame'. This topic may well end up as a future CONCEPTS: article, but suffice to say that these players are well aware of what is popular and what they are expecting to face, and so tailor their lists against the common builds. However, this can leave vital tools out and weaken their lists against other builds.
I can throw in a personal example here of my first game at the 40kUK GT heats in 2012. This was my first ever national level tournament, and so you can imagine my joy following the random pairings when I found myself playing against the reigning UK Masters Champion (actually I was really pleased about this as I had gone to get some hardcore games!). After a really good and enjoyable game, much to my surprise I ended up winning. Chatting afterwards, he said that he hadn't built his list thinking that's he'd play anyone running my kind of list. Looking back over the lists 9 months later, I don't think that the match-up was actually that bad, but I use this as an illustration that there are top players out there who bring what they think will do best in the current 'meta', and that there are risks involved with this.
Before you have even found the list, others will have played against it and identified how to beat it. The more well known your netlist is, the more your opponents will have played against it. Knowing how to fight against an army is a massive benefit, so be aware that you will be making your opponent's life a whole lot easier by netlisting.
Picking the latest GT dominating list is not an 'I-win' button! The players using those lists will know how to use them and are likely to have years of experience informing their decisions. I wouldn't expect to get into a Ferrari for the first time and win every race, so I wouldn't expect to know how to use a netlist to its full potential without practice and understanding why it works. That said, some lists are easier to pick up or more forgiving that others!
The originators of successful netlists have a good understanding of the game, and presumably didn't copy the lists from anywhere! They may have taken parts from various sources but combined and used these in a way no-one had thought of before, or perhaps have found an undiscovered combo or underrated unit. After all, the internet can be wrong (shock!), and as lists progress older netlists can seem weak and outdated. Only playing with netlists may therefore hold you back as a player.
Using a netlist as a learning tool can be really valuable, and save a lot of wasted time, effort and money. However, there are limitations to be aware of, and simply picking up a list without knowing it's context can be risky. Tournament specific lists aren't necessarily good outside of their format and meta lists go out of date and aren't balanced anyway. If you are going to use a netlist, I suggest doing your research, trying learn why it is good and how to use it, and then using that to inform your own list building and continuous improvement as a player.