TV's Frink said:

I heard that the 50 GB limit isn't strictly enforced, though I haven't reached it yet so I can't test it. Personally I'd love for you to upload to Mega, given the lack of captchas. I also use Megashares to upload stuff.

As far as I know, the 50 GB limit is enforced (if you upload a file that surpasses the 50 GB limit, it won't cancel the upload, but an older file might dissapear when you least expect it), but on the other hand, there's nothing there to stop you from signing up for multiple Mega accounts, as long as you have spare e-mail accounts to sign up with. ;)