A number of Companies have set up successfully all around pure dot com model. Take for example Google it had an idea of search engine and it made a Billion Dollar company out of it. Take for example a lot of Successful bloggers who started alone and then hired people to create a blog network. Take other companies who started with E-Mail Applications, Chat Applications and Social Networking.
Every other day there is a news about a new type of service provider giving some unique service.
The advantage of Internet has been huge on Business Ditribution. It involves a lot of effort to set up even a local distribution center but here you are with internet ready to distribute your software or publication to all in the world just by a mouse click.
If you want to sell software which requires no physical ditribution of wares then go for a Dot Com to ditribute your software product. Get into publishing business by just strating a Blog and signing up a Advertising Network and you will be able to start getting customers from all over the world without any additional investment.
Only your idea is your constraint. If you get a new idea, and are able to execute it properly you are surely going in for a good million dollars worth business.