If you've got a domain you're not using and a member of this community can make use of it I think that's good karma.
god yes that would be an awesome USP.
Anyways, about the idea, one of two outcomes is possible:
1. If they domain is worth more than threshold, someone will buy it and take advantage. I don't see a difference of a startup benefiting versus someone else reselling it. the difference in value is still being captured.
2. Garbage names, nobody cares and the site dies.
I know I am not the only domain investor reading HN and if there is quality, someone will buy them.
If I bought hotels.com and planned to sell it for money to a big hotel chain or something, I've not infringed anyone's rights. Generic/descriptive names are normally OK.
of course if there is a company using the generic for a non-generic purpose and I grab a typo/another extension and use their non-descriptive purpose, that is also squatting. For example, if I owned amazon.net and tried to sell books that would infringe on amazon. Or if I bought apple.net and sold computers. However, if I advertised amazon rain forest trips or sold apples that would be ok (not squatting).
Of course, lots of money and lawyers can change what is and isn't right (checkout nissan.com)