You ask a good question. I've seen a lot of people express fear. I've seen a lot of claims about startup being killed by patents.... but I've never seen it happen. I've been involved in a bunch of startups over the past 30 years. I have a patent myself and was involved in several others. I'm not aware of any of these patents (Which are now owned by a large company) ever being asserted (I presume that if it were at some point I'd be contacted as the inventor? It's pretty fundamental.)
I have, however, gotten cease and desists based on trade mark. I had a name that was of the type Adjective-Adverb. A company claimed it owned all use of the Adverb word because they'd registered some other two word name that included the same word. I Thought it was hilarious. They weren't even registered in the same business area as I was operating-- yet they sent me several 30-40 page threatening letters and "license agreement/settlement" contracts for me to sign via FedEx. I just tossed them and laughed.
Your assumption that people that start start-ups are stupid is wrong. People that start start-ups are in general smart enough to research the patent situation around their start-up idea and will look for greener pastures if they consider the patent situation too borked to try establishing a foot-hold or to navigate the patent minefield.
It's not just the start-ups that you see that might be killed it's all those that you never get to see or hear about in the first place, killed before they ever left the drawing board.
Start-up founders are savvy enough to take patents into consideration when they embark on a new venture, to do otherwise would be extremely foolish.
As for whether or not patents can kill companies, I've been on the receiving side of these suits and were it not for the fact that I had a main office in a country that is a bit more down-to-earth when it comes to legislation it would have certainly killed the start-up I was CEO of.
I have, however, gotten cease and desists based on trade mark. I had a name that was of the type Adjective-Adverb. A company claimed it owned all use of the Adverb word because they'd registered some other two word name that included the same word. I Thought it was hilarious. They weren't even registered in the same business area as I was operating-- yet they sent me several 30-40 page threatening letters and "license agreement/settlement" contracts for me to sign via FedEx. I just tossed them and laughed.