ECommerce has allows new types of stores to exist. Here are a few new types of stores and sellers that have sprung up with many more to come.

Niche stores
Niche stores that could not survive in any one geographic market may now be successful. No one city has enough interest in a store selling just emergency eyewash stations but now we can have entire on-line stores dedicated to this product line. The store gives users around the world access to a leading expert in the field and a selections and product information no one city can match.  No one geographical market can satisfy many of the niche stores that now can exist on-line. e-commerce stores have a national or global reach and just a few customers per geographic area would not be enough for a brick and mortar but are plenty for a store that has a larger reach. 

Really large on-line stores (amazon)
On-line stores with one website can serve one customer or one million customers. The traditional limitations of a brick and mortar store with limited stock and store space are in contrast to a web site that can have virtually unlimited traffic with little change to the shopping experience. We still have chains and big box stores such as Wal-Mart and Best Buy but they need individual stores and have limited store space, location limitations and only so many cashiers. These new large online stores can provide the selection, price and convenience most people need and can scale in ways that traditional retail can not.

Really small stores – low barrier to entry 
We now live in a time where just about anyone can set up a store. We do not need the advanced programing that we did in 1999 or the capital to rent a store front and purchase products to sell that many .

We no longer need to have the capital to purchase or rent a storefront and buy products to sell. Even in the relatively recent on-line world we no longer need the capital to hire a programmer, buy products or pay for employees the way we did in 1999. Services such as Volusion or shopify let you set up a store for $20 a month and give you templates so you need very little experience to get a store on-line. Other services let you add online stores to your current site with the additions of a little bit of code. PayPal allows anyone add the ability to pay on their own site by doing the transaction on the PayPal site with a simple link from your current web page.

Small sellers in marketplaces (eBay) 
Small stores are one thing but now individuals can sell online without having their own shop. eBay lets people list products they have for sale and Craigslist lets people post any item they have free of charge. What makes these even easier is that you do not need to be a business or have any special training at all. Just post the product. EBay takes a commission and allows credit cards while craigslist does not. These marketplaces have a low barrier of entry and eliminate much of the need to market your product because of the built-in audience they have earned.