I've come across a trolling/spam post by a user with no other contributions to the site.
I have flagged this post for moderator attention, but I'm curious: what might a moderator do in this kind of situation.
When an account is created with the sole purpose of trolling, spamming, etc, we generally destroy the account. This (as well as deletions of posts by spam flags) feeds information into a system which makes it more difficult for such people to continue posting their drivel on the site. There is evidence that upwards of 80% of all spam attempted to be posted to the site is blocked (and therefore is seen by no-one).