I guess the "taint" of a failed startup would make domain names unappealing.
However if it is a name that the general public might try, e.g. pets.com, then it could be valuable, in this case pets.com now redirects to petsmart.com.
No idea. But you could look at any one of the several domain name marketplaces and see what sorts of money is being asked for domains. Of course, the selling and asking prices can be very far apart.
However if it is a name that the general public might try, e.g. pets.com, then it could be valuable, in this case pets.com now redirects to petsmart.com.