Greg Olsen of Coghead tells SaaS vendors to buy SaaS from others rather than build their own platforms and infrastructure services. Focus on functionality and business value. While you encourage your buyers to buy, you yourself like to build even mundane stuff. It is a message similar to what salesforce is delivering with force.com.
But it is not a problem unique to SaaS vendors. As I wrote here, Software CTOs continue to be suspicious of outsourcing of even basic development and testing. Outsourcers do not like to sub-contract - why lose any margin? Telcos like to screw each other out of termination fees.
And then there is a great example of the Apple iPhone. It utilized 30 suppliers in 3 continents to get its ridiculously short 6 month time-to-market.
"Building" a "Buy" Culture is a huge need in most of technology world...
