Not really.

The MegaBox was nothing new. As Even the Digital Music News article observed:

"Actually, this is technically a relaunch of an earlier concept...

In other words, another entry into the very crowded DIY space.

The rest looks like a combination platter of cloud-based music storage, download sales, and discovery, though the elements may still be coming together."

MegaBox was no groundbreaking idea that was going to gut Universal Music, instantly. Far from anything like that. It might have had some impact but, to suggest that MegaUpload starting an online music service was "the" reason that UMG got the DOJ to go after them is just incredibly uninformed.