I doubt that many small businesses utilize more than 30% of the features in Salesforce. Most businesses would probably be just as well off with a Contact Management System. Salesforce has sensed the market opportunity and just released a Contact Manger version of their CRM.
For $9/user/month ($16 less that the next step up) Salesforce provides just the functionality many small businesses need.
With the Contact Manager Edition users can store contacts, track customers, manage tasks and meetings and integrate the system with popular email applications.
Even though $9 a month is pretty cheap, Zoho still offers a free version of their CRM. I think Zoho is really simple to use and usually recommend it to small businesses.
I would choose Salesforce if you have more complex requirements than Zoho can provide or have more than three users.
Learn about Zoho CRM.
Learn more about the Contact Manager Edition of Salesforce