It seems kind of silly to write one's own code for anything, if you have access to a well-tested library that does what you want. The only reason to do otherwise is where there is no such library. Crypto is just an example of an area that's particularly hard to get right: the solution is no different than for other things.
The problem is everyone thinks they have a library that does crypto for them --- OpenSSL or CryptoAPI. But that's not what they have. They have the moral equivalent of a small pebble bed reactor, and they're strapping it to the tops of their electric cars and hoping to go for a drive.
Keyczar and cryptlib are two libraries that offer a high-level interface that is deliberately hard to screw up. But Google Keyczar is very new (it recently had a really horrible flaw) and cryptlib is not free unless you GPL your code.
Yes; I should've specified that you should use the highest-level well-tested library that does what you want. The libs you listed (in the blog post) are definitely best-in-class for that purpose.
