They probably should be banned automatically somehow, they add a lot of noise to the new page and sometimes they last quite long.
Flagging them helps getting rid of them, the more people flag the sooner they're gone.
Also, see http://news.ycombinator.com/noobstories
Another explanation is that link spammers use something general to see if they can post 'any link' without further credentials, usually the same author will follow up with a spam link a couple of minutes later.
Some hours of day the amount of spam is quite amazing.
With HNs rise in popularity this will probably get worse, so getting rid of the spam early is an excellent way of discouraging it, and that includes such 'trial balloon links'.
http://news.ycombinator.com/submitted?id=billpg
He has been around long enough. His stories are about average, not really excellent, but there are worse stories. Yet his last four stories have been flagged to oblivion or removed by someone. I have googled the stories themselves and they were fairly OK. Can someone shed a light on this?
In general, though, please send me an email about situations like this rather than posting about it.
That is, a first post is more carefully filtered.
If an account that's been around a month and has 3 submissions that weren't flagged starts to submit one story a week... is it spam? Maybe. Maybe not.
That would make the response a lot more snappy.