We have a Ruby on Rails application that query data from Salesforce and displays the data to about 5 different public static pages. Our daily limit of API call is 15000. We have about 1000 users visiting our site each day, with this amount of traffic would this max out the API calls?
The answer is... who knows? What's more important here is how many page loads and/or callbacks you have per day, not the number of unique visitors. For example, a shopping cart built on Salesforce.com would probably run into API limits, but a simple page with little interaction wouldn't run into API problems. You might want to use some analytic tools, like Google Urchin, to determine how heavy your page is being used. Also, you might consider a local cache for items queried often, such as product listings, etc, rather than getting the data in real-time, if the number of API calls is a concern.