What about altcoins?
I've been mining FedoraCoin (Tips) and the difficulty is always jumping from as low as 50 to as high as 200. And it does this seemingly randomly, why? And what is the underlying cause?
I just did a search for you and found the announcement thread of your coin.
https://bitcointalk.org/index.php?topic=380466.0 Specifications:
Block Time: 60 Seconds
Difficulty Retarget Time: 10 minutes
So, your coin will adjust the difficulty every 10 blocks (10min / 60s = 10).
If the past 10 blocks were found in less than 10 minutes, the difficulty will up, and vice versa.