Featured YouTube Video's

I just checked on a few videos I uploaded last week to YouTube and found that 2 of them are highlighted in grey and are 'Featured Videos'.

How does YouTube choose which videos to feature?
How long does this normally last?
Is this just a bit of luck?

They say that the better the ratings the better your chances, there are also other guidelines to getting a video featured. I suppose it could be a luck if you didn't get a fair amount of good reviews or hits.