pets.com is an amusing piece of Internet history, but it is also a rounding error. For every pets.com there are thousands of companies that lost a (relatively) small sum of money and hundreds that made a small return.
actually I think pets.com might have been Hummer Winblad's first losing investment. in any case they admitted afterwards that it was a mistake on their part -- they were worried they were getting to the opportunity late and overcompensated. so it really was a classic bubble situation.