This is very good because it is going to be very hard (read expensive) to spam. As was discussed here earlier this week, using links for ranking websites incite

This is very good because it is going to be very hard (read expensive) to spam. As was discussed here earlier this week, using links for ranking websites incites spammers to create intricate link farms and, in a sense, the web is rotting from it. Typical behavior-driven ranking features (impression vs. click-through, length of time a user is on the site, number of times visited) can be simulated with clever enough bots, relatively inexpensively. On the other hand, flattr has is not only a record of websites viewed, but an actual amount of money must change hands and is a powerful feature for the social proof of a website. Granted, maybe there is a sense in which this makes it easier for spammers (just throw a bunch of money at it via flattr and you'll rank higher!) and they'll undoubtedly have to deal with spam like everyone else. But all in all I think this is a clever move and no one (in my knowledge) has tied social cash so directly to ranking.