I'd like it better if it actually were "mobilelearning.net" instead of "mlearn.net"
Even though a name like mobilelearning.net is slightly long - it basically says what it means and you don't have to do any type of guessing.
With "mlearn.net" it seems like you have to guess at what the site is supposed to be used for. It could stand for mobile learning, but it could also stand for "me learn," "mechanical learning," "my learning," "mexican learning," "metrics learning," etc.
In my opinion for this case dealing with mobile learning - it's better to say the exact thing that you mean and register the full domain "mobilelearning.net" or "mobilelearning.us" or whatever extension you chose.
That's just my opinion though.