Context: http://en.wikipedia.org/wiki/Guess_2/3_of_the_average

How could the strategy here be anything other than "pick 0"?

Even the other degenerate strategy of "pick something which is like negative infinity" is a guaranteed loser, and it's only interesting if you assume everyone else will pick positive numbers (which your web app specifies, though your problem statement doesn't).

I had 10 minutes to create the poll before the library closed...I definitely could have done a better job describing the problem, you're right.

Each person was told to pick a number between 0 and 100

The number I would pick would be dependent on who else is taking the poll, how much credit do you give them, etc

I'm in my phone now with a low battery, otherwise I'd type

The Wikipedia entry mentions this: http://en.wikipedia.org/wiki/Guess_2/3_of_the_average

But one of the problems with selecting a strategy is assuming that everyone will act perfectly rationally. This is hardly ever the case.

Results are at http://sente.cc/wsgi/number_poll/results

actually -- 'better' results are here -- http://sente.cc/wsgi/number_poll/results_unique

(the other link doesn't restrict each IP to only 1 vote)