The networks have gradually been squeezing deals for new customers over the last 12 months or so, but T-Mobile has gone a step further, reducing data allowances across the board from 1st February 2010.This isn't perhaps an issue if you've signed a recent contract, as data deals of late haven't offered much more on the network. But some people have deals with much more data included, up to 3GB in some cases. Finding your data down to a sixth of that amount is, shall we say, not going to make you best pleased.Interestingly, T-Mobile also seems to be changing the definition of what mobile browsing is too. In a statement about the change of policy, it says: '...our Mobile Broadband and internet on your phone service is best used for browsing which means looking at your favorite websites like Facebook, Twitter, Gmail, BBC News and more, checking your email and looking for information, but not watching videos or downloading files.''If you want to download, stream and watch video clips, save that stuff for your home broadband.'Thankfully, not all the networks are being so 'careful' with their data. On the contrary, the Three network is currently plugging the complete opposite with its 'all you can eat' One Plan. If you want to watch video when you're out and about or possibly download music, maybe that's worth considering when your contract is next up for renewal.