I can't speak to the technical aspect, as I'm just a member and don't get into video aspect I do have a Logitech cam. But, I rarely use it.
But, from a member's perspective, I generally don't mind when a model is on multiple sites at once in open chat. Typically, can easily tell with the ding from other sites, or how she's acting. The one thing that does kind of bother me is when she sets goals such as "Shirt off at XXXX". What happens if she hits it on one site, but not another? I think general tip notes is better, since it doesn't conflict in scenario such as I mentioned.
Also, one thing I will say is my biggest gripe about models whom cam on multiple sites: Don't play your members. Don't do a private on one site, while leaving it open on others to collect tips from the show. If I'm paying for a private, I expect it to be exactly that: Private only between us. If you want to continue generating revenue, then decline privates and stay in public chat on ALL sites.
This happened to me once, and I was pissed at the model as I was a good, well tipping regular in her room. Figured she'd have at least shown the common courtesy of closing all other rooms while in private...