I'd say defensive patents are pretty useless for a startup. The idea is to build a patent portfolio that's so large and diverse that the day some random company sues you, you just happen to have a patent that they themselves are infringing on. You also need the financial resources to pull off that counter threat. Doesn't sound like lean startup to me...
A much cheaper defensive measure is to publish your "inventions". There are companies that help you with that, e.g. ip.com.
A much cheaper defensive measure is to publish your "inventions". There are companies that help you with that, e.g. ip.com.