If 37signals apps were free...
Travis: Lots of businesses prefer to pay a small fee.  It puts a(n implicit) contract in play.  I pay you money, you operate this for me.  Free apps are scary from the POV that they could either disappear, or are insecure.Something about a company being willing to charge makes them appear more legit to other companies.  Argue it all you want, it's definitely the truth to a certain market segment.  And 37 Signals is positioned to dominate that market (although not as much as MS).