@croydon - When you consider that the olecranon process isn't the strongest of shapes and the ulna nerve placement isn't ideal either, it's surprising that more people don't injure their elbows.
In fact the nerve does get damaged quite often and I've heard that you can break the olecranon process as well. Apparently if you can extend your elbow out completely it's extremely unlikely that you've actually fractured the bone, but they will x-ray if they suspect you've fractured your olecranon process.
Elbow dislocation is pretty common as well and apparently it usually permanently lowers your flexibility. The elbow is a seriously delicate area of the body.