I used to use Mochi Leaderbords before starting coding Adobe Air games for iPhone and Android. As the Mochi API doesn’t have mobile support I had to find something else and found Playtomic. Playtomic is great and easy to use, BUT it’s constantly down 
My players are complaing on how often the highscore server is down. For me it’s like 6/10 times I try to view scores that it doesn’t show.
Anyone know of an alternative free highscore system that works with Adobe Air for mobile?