The scenario that often comes up is that a sales manager has an intern and wants the intern to do data entry or other administrative tasks in their Sugar account. However, the manager does not want to be prevented from using their Sugar account while this data entry occurs. So what often ends up happening is they ask us to give the intern their own license. This is a waste of a license, obviously, since the intern is not doing their own business development. Plus, we'd prefer the activity be attributed to the sales manager, not the intern.
We used to use Salesforce before switching to Sugar, and this was not a problem with SF. You could have two people conducting work inside of the same account simultaneously and nobody would be booted out.