The creative solution to the “double spend” problem is the valuable piece. The other pieces, cryptographic hashing and proof-of-work have been around for some time. Algorithms make up the largest pool of software patents.
If it went private (it's actually patent pending once publically released; even if CC licensed, the license is null re: invalid ownership), an owner could do what MasterCard and Visa do: percentage of transaction, etc. I bet they could even make a case for ownership of his 1+ million coins ($6.4 billion USD).
The technology is already out of the bag, though, it's not going back in.
This article is interesting re: retroactivity: http://www.toikkalawgroup.com/blog/the-patent-bargain-and-th...