There are hosts that offer unlimited bandwidth. What they mean is that they may not expect you to use more than a certain amount, as there are practical limits on most everything, including bandwidth. To claim unlimited is typically a marketing ‘hook’ to get you sign up. In reality, once you reach a certain limit, you will no doubt hear from this host to do something about this bandwidth consumption.
For example, it is as if you were to try to transfer multiple large files ( * > 1 GB ) on your home connection 24/7 for a whole month. The fact is it runs out somewhere.
Another marketing scheme is that of offering unmetered which says you can use however much the server would allow in a possible months cycle. Without a doubt the host will contact you or suspend your account.
There are some legit hosts that offer unlimited packages either as a marketing method to get their business noticed or promote it over another business. It is highly recommended that you look into your host before you sign up with them, ask them questions. If the host is really interested in you they would reply to your questions without a problem within 24 hours.
Even if you do not plan on using much space, keep in mind you are not the only one on that server and you will get other people abusing such a policy rendering you pretty much useless in the sense that you have only used a few megabytes of storage and some other person on the server is using gigabyte upon gigabyte.
Many hosts that offer unlimited or unmetered packages have fine print or policies that clearly state that if you use more than a certain percentage of the servers resources, you can be charged extra, you can be shut down, or any other consequences in relationship to resource usage. Be alert because this goes to show that the service is not unlimited and not unmetered. This can also hurt your reputation.
Also check around if you think a host is charging too little for too much. Sometimes it is a legit way for the host to get back on their feet sometimes it is the host out to get you. While the web hosting world is not full of sour apples it isn’t exactly full of sweets either.
Some important factors to check on a host when planning to sign-up: Support, Support Response Time, Server Stability, Hosts willingness to assist you with extended issues, Server policies are also important, it shows that the host is willing to reject some customers to keep the server clean and free of any people that may cause problems with the server itself (spam, virus distributors etc)
There are some features that are allowed to be unlimited however because they are just a free service to the host anyway and are run server-side. Some of these are mailing lists, mail accounts, ftp accounts, sub-domains, and databases. Databases are limited however usually because they can be strenuous on the server and drop its stability and performance.
The best way to find the information about your host is ask around, ask the host questions, look for trial memberships, look for money back guarantees and testimonials.. although testimonials may be forged most hosts are pretty straightforward about it. Ask them questions pertaining to them and such.
As a Web Host myself I do look to help myself, but I also see other hosts suffering as a result as well and this is meant to support all web hosts out there, not just myself. Who you go with is strictly your own choice and you choose who you think is right.