I have noticed that recently some answers just contain a link to a project page; the user doesn't even report what the project does, nor why does he think the module suits the needs of the user asking the question.
I would expect that who answers reports at least for which reason the module he links to should be used instead of another one.
What should we do with such answers?
Well, that depends on
the quality of the link
the perceived potential of the user who posted it
If it's an exceedingly useful link, I will edit in a quote from the link of the most relevant content, so the answer is in fact a complete answer, even if that link goes dead at some later date. This is the internet, and such things are known to happen.
If it's a user that I think has potential, I will also add a comment indicating I edited in context, and explaining why we discourage link-only "answers".
On the other hand, if it's a user that seems like a "drive-by", or a link of marginal quality, don't bother messing with it -- you should just mod flag it as low quality for removal. Or downvote to taste.
