Is that it? I was expecting something a little more scandalous.
Maybe there are way larger skeletons in his closet. It's unlikely we'll ever know for sure in this instance but I think the general trajectory of Uber has fundamentally shifted in the last month.
To be clear, the reason it's not OK is that a professional context should not also be a sexual context. It's not about protecting the person you're making out with. It's about everyone else. This is the same reason that excessive PDA in the workplace can be sexual harassment of other employees, even if both parties to the PDA are consenting.
The org chart will tell you the difference.
If I'm wrong, I'd be interested in seeing the relevant laws or cases.
It's not illegal to sleep with your boss.
Unfortunately (For your boss), if you decide to break the relationship off, and are feeling particularly vengeful, you will have a slam-dunk sexual harassment case against them.
Good luck to your boss proving that the bad performance review they gave you was not retaliation for you breaking off the relationship.
Or, likewise, good luck to them proving that the good performance they gave you (But did not give Billy) is not based on you sleeping with them. Billy will also have a pretty good workplace discrimination suit for to bring, there.
That's not entirely true. If the relationship is long-term or it's public knowledge, the risk of this is much lower. Secret affairs? Very risky. Open serious relationships? Not as risky (which is why companies that allow relationships generally require that they are disclosed). But still too risky.
The discrimination suit is more risky in each case, because you'll pretty much end up trying to prove your innocence because you'll look guilty by default.
It's a big risk to take! Especially when the alternative is one of you moving to a different department.