With $5 million, the investors/founders believe it can be at least a $10 million dollar company in the next 5-7 years. I personally wouldn't have made that bet but at least they are charging money for their app.
I figure that if you take VC money you believe you can build a company worth $100 million.
Granted VC David Hornik in the following video is referring to revenue potential, I still think that what he says implies that VC's are looking for investments with potential exits far greater than $100 million.
To clarify I meant that as a lower bound. In other words, don't take VC money unless you believe you can create a company worth at _least_ $100 million.
Completely agree that the team is very important in getting funded, but so are connections.
Yammer is Founders Fund backed. 3 of the 4 partners from the Founders Fund are PayPal cofounders (Peter Thiel is the big name, but there's also Ken Howery and Luke Nosek) - Yammer's CEO David Sacks was the COO at PayPal before its acquisition.