PPC engines who pay spammers?

who is it?

[watchthis]

Hi guys. I am sick and tired of blackhats link spamming all my sites.
Their links seem to lead to PPC listings for pills and a gaming keywords.

Firslty, which unethical ppc company is feeding these thugs?
Secondly, as an advertiser how can one allow this to happen with their ppc budget.

Your feedback is appreciated.