This seems foolish.
Better tell McDonalds, IBM, Target, HP, GE, Pepsi, Coke, Home Depo, and Berkshire Hathaway they are now too big to fail.
Oh and dont' forget google, they have more than 20,000 employees, better break them up.
Actually why not just look down this list to see just how foolish your 20,000 person proposal would be:
http://money.cnn.com/magazines/fortune/fortune500/2012/perfo...
Note that by the time you get to company 49 they still employ more than 126,000 people.
EDIT Sorry I guess my point wasn't clear. My point is that employee size is a very poor measure of a company being "too big to fail".
Let me lay it out like this. Consider a fictitious burger company with 20,000 employees. With 50 states it can only employ 400 people in each state. If it went bankrupt it's very hard to see how this is "too big to fail".