It isn't really necroposting if you are attempting to bring the thread back to life. Now, if you are just answering someone's question/comment from five years ago, then it is really annoying.

I can just imagine things like this happening,

C3PX (back in 2005): So, Microsoft just announced Windows Vista! Windows XP was pretty good. I bet this Vista thing will be awesome and really show those Apple users a thing or two. PC users FTW! I'll definitely be trying it out when it is released.

C3PX (a few days later back in 2005): Wow, no comments? No one?

Fink (five years later in 2010): Dude, what are you talking about? Vista sucks!