JP proposes the following mantra for buy versus build technology decisions (building something inhouse versus buying a commercial product:

"If the problem is generic use opensource
If the problem is specific to a market segment use commercial
If the problem is unique to your organisation use your own resources"

Buy versus build decisions are often complex with political ramifications.

If you make a build decision, you often need to decide on whether to outsource and if so, what to outsource. When it comes to outsourcing, I use the following broad pattern of thought:
-Think deeply about the role IT is playing in your business today, and where you see it going tommorrow.
-Look at your application portfolio and your people capabilities in relation to the role you see IT playing. That will tell you where your crown jewels are and also point out your capability gaps.
-Use outsourcing to fill capability gaps in such a manner that your own people can polish your crown jewels.

Enough said for a Sunday afternoon!