Wow!. I just want to say I'm completely amazed by the quality of the answers and the discussion that my post generated. I'm not gonna be able to check back until tomorrow night (another big part of the crappines of my job, heavily restricted Internet access).Thanks a lot to everyone for the time they have taken to participate.
I dont know, I have worked in some very big clients and I just dont see them trading their ERP's for some startup product, they just have too much riding on it, without counting the HUGE piles of money they've already invested in the SAP solutions. Its like the mob, once you're in you're in and the cost of getting out would be really steep.
On the other hand, and this probably was what you were actually going for, startups could provide an alternative to those very expensive solutions and could very well tap into a huge pile of money thats sitting there waiting to be picked. One corporate client can generate more revenue than 100 freeloading "social users".