Note that it makes sense to delete submissions so that the set of submissions associated with you is not too large (so that the score for each submission is not too low).
Why not just tie it to their FICO score for yet another more random solution? At least the person can have a life outside of solving esoteric puzzles all day long.
Besides I don't see a strong correlation between users ability to solve a puzzle and their ability to find and post interesting content. Which would result in a pretty random front page...
I've got my hands full starting a company.
I hate to sound negative, but I don't think that the folks who have that time to solve puzzles have the appropriate judgment to figure out what I might want to read.
Moreover, if they have lots of time to play with puzzles, maybe they have lots of time to keep up with the latest news as well.
This looks like more of the same. I'm not interested in pretending that the ability to solve puzzles is some sort of overall mark of quality, instead of just a specialized skill that is irrelevant as often as it's relevant. I've had more than enough of that attitude. I spent years in high school and college being exalted for my skill at constructing complex solutions to toy problems, as if SAT scores were the true measure of wisdom, or competence, or virtue. They aren't.
Though it would be funny to see porn sites have you solve a puzzle to view some pics :)
I think you should make it truly merit based - submit a bugfix or a feature patch to an open source project to post a link :)
As for puzzle solving, you can make the puzzles really difficult to eliminate the vast majority of spammers.
Moreover, as suggested by gaika, one can use merit points from useful contributions to society instead of puzzles/games (e.g., contributions to open source projects).