Not trying to be a jerk, just trying to educate a bit on webshosting.
The account you have is on a shared server. They pack on as many accounts as they can with the resources onto one server. This is not a bad thing if all you are doing is hosting sites, though be sure to read the fine print on the TOS.
They advertise unlimited space and bandwidth though they reserve the right to cancel your account.
Usually it works out that if you are running a program, such as a high traffic message baord that is extremely resource intensive on the CPU and memory, they will tell you that you have to upgrade to a higher account because you will bog down the server and the other users on it.
Usually if a server becomes too overloaded they will take a look at the people who are using the most bandwidth/space/memory/cpu usage, and knock off the highest user and replace them with another lower user. This way theya re making the same ammount of money but their server is using less resources.
Like I said the common user will never use that much resources and these offers are perfect for them, but jsut wanted to keep you all informed of the misconceptions of unlimited offers.