Vodafone (NYSE: VOD) is making a play for the social graph, unveiling a Facebook App that acts as a web-to-SMS gateway. Called Vodafone Connect To Friends, the app integrates with Facebook’s contacts system to let users send messages to friends’ mobiles, if their profile contains their number; but it can also send to non-Facebook users’ mobiles by creating a new contact. Later this month, the service will expand to let people send pictures from Facebook as MMS messages.

If you think this means an SMS free-for-all, however, think again: whilst users get 25 free messages, thereafter users must fill up with premium credits costing £0.10 each ($0.17), whereby SMS uses one credit (£0.10) and an MMS three (£0.30). So the whole exercise merely shifts the message sending from the handset to the computer. Vodafone Connect To Friends is not limited to those on Vodafone’s own network but, as it doesn’t appear to sync up to Vodafone accounts for those who are, it means Voda customers have little incentive to use the premium-rate messaging from Facebook and every reason to use their bundled messaging allocation on their handset.

Still, this is billed as a trial - it’s one of the first projects to come out of Vodafone’s new UK internet services division and was developed along with IBM. The service is only available to those in the UK.