It comes from the financial industry, and means a million. M stands not for million or mega, but for mille, which is Latin for a thousand. So it is in fact 1000*1000 = 1,000,000.
It's common in finance ... in theory it's supposed to mean "thousand thousand" but I think that's retroactive reasoning for something of a goofy abbreviation.
They have mentioned only youtube on home page. If they do not have integration with vimeo, I won't call it good because Vimeo is being used lot more for commercial purposes. May be for their easier terms and conditions. .........That's where analysis will be more required. Youtube and Dailymotion already have good analyitics information. http://syncfin.com/youtube-vimeo-dailymotion/
MM? Does it mean mega million (ie 10^6 * 10^6 = 10^12, otherwise known as a trillion)? If you take the SI system it might be megamoles perhaps?
If someone has a justifiable reason for using MM to represent million, I'd love to hear it.