Auratious Taak commented on this thread in response to Rarkthor who indicated that he took Missile Launcher Longfangs before it was a "fad."
"For the record, i know a bloke who took Missile Toting Long fangs in 2nd ed onwards to now. What is your point here? That wow, you take an obvious unit choice just like a good chunk of space wolf players the world over? *claps* Also, fad implies it will become obsolete. Unless ML's become stupidified in the future it's hard to imagine LF's w/ML's becoming unpopular as a points efficient unit that fills a vital role in a SW army."
A few things here. "Fad" implies that lots of people are doing something because lots of people are doing something. In this case I think lots of people are doing something because that something is obviously good. Longfangs have a very points efficient unit in the Missile Spam Longfangs.
That's not really that interesting. What IS interesting is what happens when a codex comes out and gives people a tool, like Missile Launcher Longfangs. They get used to having this tool and then start taking something similar in other armies too. After Space Wolves came out you saw more Missile Launcher Devastators of all kinds, as well as Missile Launcher Havoks in larger numbers. Now I'm not saying that no one did this before, because people did, but it became much more mainstream.
Now, after Grey Knights came out, you see more people taking Bolterbacks. Even though "normal" Bolterbacks aren't as good as the Grey Knights version, you suddenly realize what it means to have 18 = 27 twin linked long-range anti-infantry shots in your army. Even if they are "only" wounding on 3's instead of 2's and don't have quite as much anti-mech utility. So you see people like Stelek sticking Bolterbacks into Space Wolf armies, people putting Bolterbacks into Blood Angels armies, etc.
While they may not be "as" good, people see that they are still good.
I find this phenomenon interesting. Thought maybe you guys would too?