It really depends on the individual case for me. I'll delete it if its of low content, and if its particularly a problem I'll message the users involved.
Ugh. I wouldn't want your job. The problem with what MagicSmoker is talking about is that these posts look
just enough like legitimate ones that you'd be hard-pressed to state with 100% conviction that they're not actually people responding to one another.
What can you expect when you hire someone to bump your ANN thread? If it's completely obvious that it's being bumped with "great project" posts, the entire thread might get shitcanned. This way, it puts enough doubt in a mod's mind (if it's even noticed) such that the thread stays alive--and always on top.
There will come a day when the ICO market crashes. People are going to figure out that most of them are scams and that there's no money to be made by investing in them. When that happens, none of this is going to be a problem anymore. Can't wait till then.