Prok-
Think, if someone wants to do something nefarious they do not need to talk about it. If you are using a copying tool you already know how to use, why do you need to communicate in SL about it?

I will play along for a moment and say they do though. "Oh, SL will not let us communicate privately? I guess we will use some outside tool that does then."

Meanwhile, customers are akin to noobs in some ways, they need to be treated with kid gloves. You want to make it easier for them, not harder. If they can hold a confidential conversation in the tool they are using at that moment they are more likely to stick around. If you tell them to do something else they might say "nah, I will go with another vendor".

I hope you are not on a jihad to ban all of emerald. If you are, a lot more people that did not already know you will be against you. Emerald is probably the most popular browser after the SL clients right now.