Yeah yeah, pets.com blew up. Banks have gone bankrupt before, too: that doesn't mean banking can't make money.
That's not to say that it's a good idea to start an online pet food business now. By now the margins must be pretty low. But it is an "old" idea for which the market is still big.
Exotic pet food (Squids) + supply's + information. Bulk shipments of food + breeder information for show dogs.
PS: I have a friend who has been making good money selling cookies online. It's a classic small business with a few workers in a low cost of living area, and it's been steadily growing for a while now. (http://www.thebestcookie.com/) There secret IMO is simply high quality and high minimum order sizes.
This is a huge duplicate content issue, and there are much better ways to target multiple keyphrases.
The specifics relate to the market and the kinds of product sold. You are not going to make money shipping individual 50lb bags of dog food to people, but you might be able to make money shipping pallets of dog food to people. Things like building communities or creating content are really just another form of advertizing that is theoretically cheaper to create in the long run than Adwords.
Nope, IMO it's f*cking perfect. Having worked for a book distribution company: the item is easily packaged, it's easily identified by the purchaser (no brand confusion), it's easy to use with no support costs, all items from the publisher are sale-or-return - any excess inventory goes straight back to them rather than clogging the store's shelves if it doesn't sell. Amazon also used the Internet to overcome the traditional problems with book distribution: which titles to carry and market, because there are so many. Just carry all of them.