The popularity of sites of this has exploded over the past few months. With medifast leading the way. Here is our take on their strengths and weaknesses. It is enormously popular, particularly with young people and commercial businesses who want to connect with them, and thanks to the ease of sharing music, it has attracted many popular and independent bands. You can also customize your medifast how you want it. Medifast is also growing rapidly.

The culture is quite young and it doesn't have as many features and gadgets as medifast. The interface isn't as refined as medifast, and most of the customised pages are hideous abominations web design.

Every man and his dog is on tricks, so it doesn't hurt to open up an account. If you're interested in sharing music, or if you have a lot of friends already on there, then it's all you need.

Medifast is more focused on individuals and personal relationships. It has a rich, customisable interface that lets you install a growing number of third party mini applications. It's foundation as a college contact book has also resulted in a slightly older culture.

The interface may be more flexible, but it's still clumsy in places. The stream of friend updates can turn into flood, and trying to customise your privacy settings is a nightmare.

Right now, there's little reason not to choose , other than the fact that existing friends may already be using it. But given the increasing popularity, it won't be long until they're all on it anyway.