When you take one physical port and expand it's connections, you are increasing the workload for that one port (and forcing it back to the system) and all of the communication that must occur on that port. Problems could occur due to speed, amount of data, power requirements, devices and drivers, etc. Think of a neighborhood with one house and one water line - and now there are 15 new houses all needing to use that same water line.
Do you think 2 Behringer $30.00 sound cards and a mouse would be too much all together one 1 USB port?