At this point, it’s basically a human-rights violation to do so.
When two exchanges eye each other from across the ocean, there's a pretty standard courting procedure. One or both have usually been spurned and lust after a deal, if not particularly with the available lepers, then after a deal for a deal's sake, just to show they've still got it. They dance around each other for a while coquettishly, before agreeing that it really would be a great idea to spend their lives (or a convenient period of time) together. Then, the regulatory chaperones step in and, usually, say no.