Millions of accounts, yes, but how many of those are people who play modern "AAA" games and who won't want to look elsewhere for new releases? That's the question. My girlfriend is two of those accounts and all she owns are Popcap games.
Who knows? If it's even as low as 10% (which seems very low) it's still totally ridiculous from a sales potential perspective even at whatever percentage Steam takes per copy.
I would agree in that if they notice significantly lower sales they will reverse course rather quickly. I don't think they would release BF3 or ME3 on PC as experiments though. They are expecting high sales on the PC for BF3 at least, based on Bad Company 2 sales. I wonder how big a percentage of BC2 sales came from Steam.
That's why I agree with Krovven that it's a poor decision if that's the case. The amount of great games landing in November this year borders on the absurd, I have something like $400 to spend if I want to own them all. They can't really afford to mess around with this stuff if they are counting on the sales. If I was an EA shareholder I wouldn't be happy about it. Thankfully it's still pretty early so hopefully it gets ironed out beforehand.