Your idea about getting closer to 50% probability of an upvote in order to get more information identifies a weakness in the voting system. It doesn't matter as much for comments, but I think it is inadequate for articles.

Much better than having to put every article into one of three categories -- up, down, or neither -- would be to have a slider that starts at 0 and can take values between -100 and +100. What we have now is equivalent to something like having -100 to -33.3 all mapped to 'down', -33.3 to +33.3 all mapped to neither, and +33.3 to +100 all mapped to 'up'. Obviously, lots of information is being discarded by design.

Another problem is that votes aren't normalized with respect to the user that cast the vote. An up vote from a user who rarely votes up should be worth more than one from someone who votes everything up.

Also, there could be distorting effects due to different subsets of readers preferentially reading different subsets of articles. If readers coming to LW without having read OB tend to vote differently (which is plausible since OB folks have not voted for years and may think of not voting up or down as the default, with a vote being for special emphasis), and they tend to read different sorts of articles (simpler articles on easier topics), the articles they read will appear to be wildly more popular.