I don't know how many sources are contributing to the spam we've been seeing, but it's obvious that there's at least one. I just posted a comment in a spam thread that was started by someone unknown source, and within seconds, a brand new spam thread appeared along the same lines.
It could be coincidence or it could be that whoever is posting this spam is tracking it. I see that each thread has an RSS feed so it's technically possible to track them for updates. And while I can't prove it, it's not outside the realm of possibility that an update could trigger a response for more spam.
So I guess the bottom line is, don't feed the spam trolls. :-S

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