A great blog on the IT in large enterprises or Government. The author starts out with the interesting story of Tinman from The Wizard of Oz. He explains how a package acquired and gradually modified to meet an organizations requirements.
In principle, buying instead of building is a great idea — it lets a company share development costs with many others while concentrating its limited IT resources on its core specialties. This approach works, however, only when a product does something that is well understood and widely implemented (i.e. it’s a commodity).
He has some advice on how to avoid this problem. I think publishing the interfaces to the core application services is definitely one way to mitigate this problem. Look at the rapidly increasing mashups and the Web 2.0 applications and you will get an idea of the future of Enterprise Application Products.