Not wanting to be rude or anything, but I can't see the utility on such messaging service. If it's just backing up some data, you can do much better using services like Wuala...
Are there more such services?
Sure. Anything that you can't legally or safely do with conventional electronic means of payment is a niche for bitcoin, and there are many. From illegal trade to anonymous investments, and all sort of tax evasion techniques daily performed with cash, now can be done remotely. Avoiding labor laws while hiring someone remotely is another option that just came to my mind.
The great majority of these are perfectly ethical. I don't think we should be ashamed of promoting bitcoin usefulness for these kind of things.