The advantages to this are obvious, the site is free, there is very little time consuming maintenance, and the mission of the site can be fulfilled if it is one that is limited. The disadvantages are not so obvious. In the web world you are not considered a serious player unless you own you own domain name. There are too many web savvy people these days that instantly dismiss a nested site, or at the minimum don t take a nested site very seriously. Whatever they come looking for, it helps to be able to deliver it.
Good content is like giving good service, it generates word of mouth advertising.
Soon people are going out looking for you on the web. Be warned though, good content can cost a lot of money. Getting a good web designers can cost a fortune. This is one of the clearest examples in life of getting what you pay for. Think it through.