The general category is called ASP's or Application Service Providers. This is currently being done in the financial field by Quick Books and Netledger for on-line accounting packages. It is also being tried by some Office providers. Some of the advantages of using this system is that you always have the latest version of the software, do not clobber up your hard drive with large programs and have access to your files from any computer. Files are stored on-line and passworded so only you have access to them.
Prices vary from vendor top vendor.
The basic ThinkFree service is free. The software and on-line use cost nothing, so the price is right. The disadvantage is that you need to have a broadband connection and wait each time you sign on for the system to check your computer for updates needed. Enough of the program is placed on the computer you are using to be able to work off line, but the file size is small. Supposedly the system will read and write MS Word files to maintain compatibility with other users.