Despite all the interest from VCs in mobile gaming and big revenue estimates, the true demand for mobile games hasn't been clear. But a new study says that just 27% of US mobile users play games, up from 20% last year. Just 6% of non-gamers, though, said they had an interest in starting to play over the next year, and just a third of mobile players actually buy their games, with the rest happy with free or pre-loaded ones. The study says the average gaming session is a "mere" 11 minutes and the top motivation for playing is "to kill time or alleviate boredom" -- so it looks like the idea of casual gaming is for real.