A new Nielsen study on mobile social networking finds that 4.1 million US consumers, or roughly 1.6% of mobile subscribers, accessed a social network site from their phone in December. The UK had the second-highest number of users in the countries studied - 812,000 - but slightly edged out the US in terms of percentage of users connecting to a social network via a mobile device.

With 1.7% of its mobile consumers engaging in mobile social networking, the UK has more than twice the percentage of its mobile subscribers using their phones for social networking than the other European countries surveyed - Italy, Spain, France and Germany.

It's not really surprising that MySpace, the leading social network on the PC, is also the most popular among mobile users in the US. According to Nielsen, MySpace logged 2.8 million unique mobile users in December in the US, followed by Facebook with 1.8 million.