100% on GTAIV is single player only stuff though, and there are people on my friends list who have Let Sleeping Rockstars Lie. So it can happen, although its pure luck.
The fools at Rockstar should have made it viral really. Kill someone who has killed someone who killed someone who killed a rockstar dev.
EDIT - Well according to a few sites I looked at, this achievement *is* viral... I'm sure the same guides said it wasn't a few weeks ago.
Anyone got the guide book? Viral or not?