You could remove all posts with less than one wheel from search index generated pages, that would defeat what spammers are trying to do but im assuming they arent making special spam bots for hubski, hubski is just getting caught in net.
I would propose that new users not be allowed to post new topics until they get a certain number dots in their wheel (and that dots given out by new accounts dont count until the wheel is full at least once) .
My criteria for post showing up on global are:
Any post with 2 wheel dots:
Any post by a user who has earned at least a wheel:
Only users who have earned a full wheel can give wheel points that count:
Only topics above are generated to search engine spiders In fact i would probably raise the dot threshold to 3 or 4 for search engines.