also note, many sites will say
Unlimited GB's of Space
Unlimited GB's of Transfer
Unlimited Domain Hosting
Unlimited E-Mail Accounts
Unlimited MySQL Databases
its never true on shared hosting, read Terms and condition for those for details, but it all matters regarding size and growth of your site
Also there is limit of number of concurrent connection to a site at one time, mostly its limited to 25, godaddy gives 50, so consider that as well.