With as little as a couple hundred unique visitors on a website, we were seeing close to 300 SQL logons per second coming from Commerce Server. Every hit to SQL was creating a new connection. Luckily, this is a quick and easy fix to get Commerce Server to start reusing open connections to SQL by using connection pooling.
Take into account though, if you are using impersonation on your Commerce Server website then this is a security risk. If a one user reuses the SQL connection of a different user, they can assume the security rights of that previous user.