In general, insurance makes a lot of sense when the events that are insured against are catastrophic and statistically more-or-less independent. Health insuranc

In general, insurance makes a lot of sense when the events that are insured against are catastrophic and statistically more-or-less independent. Health insurance is the canonical example. Insuring against events that are likely to occur to every insurance holder simultaneously is much more difficult. AIG, for instance, collapsed when lots of people called in their "mortgage value insurances"; a more paranoid underwriter would need to sit on a huge pool of money until something happened. Other constructions are possible, but a patent troll targeting one small developer is likely to target so many small developers that actually fighting all those lawsuits would bankrupt everyone. You'd need a few big fishes in the pool to absorb those kind of shocks, and I think the Googles of this world prefer fighting their own battles.