If theymos wanted spambots to keep the forum active, he could just as well make them by himself. I doubt he's into that.
True, but there is an obvious change in how plagiarism has been dealt with on the forum. Previously, users were permanently banned for a single copied sentence, even if it happened years before being caught (which was imho the wrong approach). Now, spammers are not being banned even after multiple plagiarism cases and this coincides with decreased forum activity.
If you have to speculate, what would you say is the reason for this change?