@Barnaby
Barnaby, unfortunately two problems with this
a) courts seem to take the stance that if the PTO approves it, you must prove that the patent is wrong. Meanwhile
a.1) PTO's assume that courts will sort it out, so don't work too hard to see why a patent needs to be approved
this means
b) you have to take it to court and this is expensive. Especially since courts demand you accede to their filing procedures even though you are unable to know what they are and how to apply them (so need a solicitor, who needs to be better [hence more expensive] than their solicitor).
So although you may be able to make up a really GOOD defense, you can only apply this in court and the patent troll (effectively, because the patent is ridiculous) will ask for less than the cost of defense.
Patents are only sensible on REAL objects, not software or algorithms. The reason for this is simple: real life can bite you in the bum severely. An example may help show how:
Set up a gearing system that uses a lot of gears and covers a large range of gearing ratios.
On paper or as an algorithm, this will ALWAYS produce an answer that works.
Implement in real life and you have problems with backlash and gear resistance. Your patent would be on how you changed the optimal paper solution to overcome these problems.
Software has no real life bite-in-the-bum scenarios.
Algorithms have no real life bite-in-the-bum scenarios.
When you apply your software analogue to a real system (like the gearing problem: use it to work out how to create the gears that will do this and then cut the gears), you get bitten. And that may be innovative enough a solution to afford social value to awarding a patent.