My vote goes to yay, but if they are easy to get, then MAYBE throwing a few of them in wouldn't be too bad (as long as it can be done split screen or something).
Armored Core: For Answer has achievements for 1,000 kills/wins online, 2,000 kills/wins online, etc. in increments of 1,000 up to 5,000, then 7,500, then 10,000. Not only is that insane to achieve even if the game's online wasn't deserted, but those achievements are just far too demanding even under normal circumstances.
However, Vampire Rain had easy multiplayer achievements, the most difficult one requiring the player to kill three people in thirty seconds as a Nightwalker, which even then isn't too hard to get as long as you pick a small level and your friend can distinguish left from right (Yes. This was a problem when I was helping two friends with it. I wish I was joking).
As a whole, though, I say yay. Enduring the idiots of Xbox Live isn't worth 20 gamerscore for shooting down an AC-130 with a frisbee or whatever.