There really isn't much reason to fear using credit cards on the net. In comparison, getting a refund when you paid cash or after your check clears can be quite an ordeal. Besides shopping for your household, you can also shop for kids away at college, or their grandparents, or send your order ahead to your vacation destination where groceries may be harder to find or more expensive. Travelers staying at efficiencies can also easily outfit their pantry this way. The Netgrocer system takes a little getting used to at first and may require a few sessions to get acclimated.
Selections are somewhat limited.
The prices are competitive especially with metropolitan and remote areas, but not always as low as my local supermarket in the Southern California suburbs. Prices are lower for big cities, remote and resort areas. Delivery costs are lower than a typical round trip drive to your local grocery store. And the service offers a convenient way to do your shopping, especially for recurring items and special circumstances. On balance, there certainly seems to be a market for this service.