In what way?? Basically if you actually (even accidentally) select one, they have a habit of crashing the Humax. Yes, they do reappear each retune, but I don't let mine retune any more often than is strictly necessary, and I strip out all the crap services when I do (group select and delete).
There are several available on Freeview, "Connect" for example. They are listed HERE (click) as "streamed channels" - the broadcast data just tells the receiver box to go fetch from the Internet. They cause so much havoc with the HDR-FOX users are well advised to delete them.
I do not imagine there is any immediate danger to the normal iPlayer.