AWS Certified Solutions Architect Associate Test 6

Public (IPV4) internet addresses are a scarce resource. There is only a limited amount of public IPspace available, and Amazon EC2 is committed to helping use that space efficiently. By default, allaccounts are limited to 5 Elastic IP addresses per region. If you need more than 5 Elastic IP addresses,AWS asks that you apply for your limit to be raised. They will ask you to think through your use caseand help them understand your need for additional addresses
http://aws.amazon.com/ec2/faqs/#How_many_instances_can_I_run_in_Amazon_EC2