Originally Posted by xbskid
I think it would be trivial for them to write their own code.
It's not a trivial algorithm. There's a legal format for addresses that no user would ever enter (unless they're an accountant or something). Things get re-arranged from lines 1,2 and 3, certain words are capitalized, and the information is consolidated for accuracy. If you give it an address and a state, it can generate your full postal code (beyond the first 5 digits). If you give it the wrong information, it can correct it and will return error codes along with it's best guess at the address (this is handy for correcting spelling mistakes).
I was working at a company with around 60,000 employees, 5,000 developers and a huge Not-Invented-Here complex. Yet we still did not try to re-write this service, so either it was cheap or just way too much effort to duplicate.