Now that social media has established itself as a medium, there’s a bit of a shakedown going on among the various players. Who’s the king of the hill?

According to a new study, into mobile usage among 16 to 35 year olds, the answer is Facebook, which turns out to be more popular than Bebo, MySpace and Twitter combined.

The comparison with Twitter is particularly interesting. While a third of young people regularly access both Facebook and Twitter via their mobile, they prefer Facebook. According to the 15-year old intern who wrote the report, ‘teenagers realise that no-one is viewing their profile, so their tweets are pointless’.

That’s perhaps not a reflection on the value of mobile social networking itself, so much as its value for particular users. I’d guess the same age group is likely still to follow tweets from high-profile individuals, celebs or brands they are interested in.

There are some other interesting points in the study, by mobile research firm CCS Insight. Younger users, it found, are the ones most likely to buy content on their mobile phones. There was a heavy (2:1) skew towards males in its sample.

The company also predicts that by the end of 2009 some 44% of mobile users will access data via their handsets.

More details here.