It's also worth noting that the burden of proof is on the alleged infringer to convince a court that the patent is invalid. Invalid patents can still cause pain.
Indeed. Attention is given to patent trolls, but not so much (that I'm familiar with anyhow) the incentives around awarding (there are incentives in place to bias the granting of a patent, as opposed to denying one or claw back clauses regarging wrongly granted patents) or voiding patents.