What does this mean?
It means that traffic doesn't count for much - you're going up against those with more money than you. Just like many systems, Entrecard has caved into the demand for the wealthy users to buy their way up the system. That means that normal users have literally no chance to get their ads on websites with high levels of traffic - because now that people can just buy credits, they will blast up the cost for advertising on those blogs.
Google goes in one direction by penalizing those who try to game the PageRank sytem, while Entrecard encourages people to buy their way up to the top of theirs.
What's worse about this horrible, greedy decision by Entrecard is that they're literally saying, if you put a widget on your site, we'll find advertisers and take all of the earnings! Sounds fair!
If you don't like the idea, then remove your Entrecard widget. I've already started thinking heavily about this.
Thanks for selling out, EntreCard!
Update June 4: Problogger drops Entrecard.
Update July 9: Tyler Cruz drops Entrecard.
Update August 15: John Chow drops Entrecard.