To me the problem isn't really the length of the patents - if they are used and licensed reasonably, they can last a while without harm
As has been said before the two big weaknesses:
- patents granted that are too vague, too generic or too obvious. Let's assume patent offices no longer employ Einsteins and outsource a lot, and it shows... I mean, 1 click checkout? Blatant in computer related fields but increasingly happening, it seems, in biotechnology where patents have appeared for things like crossing two broccoli varieties by cross pollination... you know, the traditional way?
Companies have been quick to take advantage of that, with pragmatic reasons (i mean, most dont set out to be evil, just doing everything they can within the system to defend their business, which everyone would expect them to do) - after all if you dont do it,
- patents that the owner does not work or license, or at prohibitive rates. How the system should cope with this without overly infringing on the rights of business owners and inventors too much, and without turning punitive for the small operation (it can take a lone/small business inventor a while to get an idea ready for market) *is* a challenge
aside: a very damaging example of this are patents that are there to prevent competition that might be based on new, emerging techniques. Companies in health watch the publications and apply for vague patents on "the use of new technique X to the treatment of condition Y" - where they didnt invent or pioneer X and might not be researching its applications to Y, just defending a product they have that tackles Y's symptoms.