Will users adding their own switches cause my network to slow down?

I'm wondering if there's any downside to users plugging in their own switches to wall jacks to hook up their gear?This is an example of what I'm dealing with:https://i.imgur.com/NiR7ITG.png

Sometimes the users have more devices (mostly QA teams) than there are network jacks so they put little 5-port switches in jacks. Is this going to affect my network badly in any way?
Edit: Besides the possible loop and more devices on the network causing more traffic.