Current patents are not about exchange of knowledge (I'd ask what have you been smoking, but it's against the HN guidelines, in your view the patent trolls must be the bringers of fire) - Apple patents on rectangular form, Monsanto and Co patents on genes, the mind blowing obvious software patents.
Now THAT is an easy one. You make your game multi-player online and host all the IP on the server. That is the alternative that the world is being pushed towards. Perfect DRM, and less power in the hands of consumers than we have ever seen before. (Playing it offline or after the company has gone out of business? Forget about it.)
However, it seems like most fields are integrating improvements from computing so there is a lot of low hanging fruit out there.
Poor implementation in your jurisdiction doesn't make the idea of patents wrong.
Maybe something like http://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welc... or a video codec like H264.
Though personally I think the wording of UK patent law by the letter rules out patenting of such algos (that's always bugged me a little), but you asked.
I think the notion of being expensive to develop is misguided as a test for worth of a patent. Similarly the question of whether it 'needs to be protected' (paraphrasing you).
The question should be does it serve the public to stimulate the free exchanged of ideas in this way; does it promote useful technologies; does it encourage innovation.
[Aside: My preference would be for a shorter patent term to reflect the faster pace of technical change. I'd also bring copyright terms in line with current patent terms as a maximum period.]
I think most programmers will take industrial secrets over patents in the blink of an eye. Patents here are things that any programmer can come up with if they spend a few weeks working on.
Personally I think he'd release his treatise under CC-BY (which requires copyright law to work).
FWIW patents are about an exchange of knowledge for a time-limited monopoly on the use of that knowledge. Patents allow the free propagation of the ideas behind patentable inventions and provide means to incentivise inventors and to reward beneficial inventions. They also, by exclusions, all the development, experiment and investigation of others in to the content of patent disclosures before the details therein would normally be disclosed.
The alternative to patents ("open [letters]") is industrial secrets. If you can show me how making all current patent disclosures in to industrial secrets promotes the propagation of technological ideas I'd be much obliged.