Maybe they're having problems with their new system that they implemented? I wouldn't worry too much anyway, it's not like Alexa is particularly accurate, our site is getting more traffic than ever before but somehow Alexa doesn't think so...

Seems to fall behind for days/weeks sometimes without getting updated. I think they should rename "yesterday" to "Some day in the last month"

for being so off on stats for any site smaller than top 1,000 and being way off for those as well ... I don't understand how the service ever was bought for $250mm

It was 1999.