http://www.spideroak.com has been doing this for years. Nothing new to see here.
Here's a list, taken from (http://www.kimpl.com/1297/secure-online-backup-file-sync-ser...) which also has some reviews.
(https://www.syncplicity.com/)
As others say, there's a difference between syncing and hosting; between levels of security; between ease of use; etc.
And obviously Tarsnap is great, for people who know what they're doing.
Mega offers everything wrapped in encryption, so presumably, his company will have plausible deniability (zero knowledge) of the files/folders that his service is being used for.
From a technical standpoint, I also believe it makes de-duplication impossible but someone with more knowledge on that subject can comment on it.
(https://www.dropbox.com/help/27/en)
> Dropbox uses modern encryption methods to both transfer and store your data.
Sure, you're right that the difference is that dropbox holds the keys and mega doesn't. But you're also ignoring the fact that Dotcom has had considerable interest from law enforcement in the past, and that some companies have cooperated with law enforcement by pushing malformed client software to some customers.
Spideroak is for your own private storage (+ShareRoom for sharing with a group), MEGA is positioning primarily for filesharing.
Yes, they both use encryption for files without sharing the key with the service provider but that's as far as I'd go with the similarity.
http://images.macworld.com/images/article/2012/09/spideroak_...