Even if Mark had remotely turned on the camera of his own computer and started recording, I doubt wiretapping laws could come into play, because it's a) his property (see also: case law involving video recording of employees) and b) he's not law enforcement.
What it would come down to is reasonable expectation of privacy, but considering the admission that the laptop was stolen, most judges would throw this whole thing out if privacy was the legal argument. Any thief would know that a person whose property was stolen would probably go looking for it.
Mark's first amendment rights to publish data that is recorded on his property trumps the alleged thief's expectation of privacy.
The other issue that could come into play is copyright, but again, Mark is the owner of the property. Photographers who shoot photos on company equipment don't have the copyright of those photos; the publisher does, unless there is a specific contract between the author and the publisher granting the publisher (or the author) reproduction licenses.
Lastly, others have mentioned libel/slander. There's one flaw in this argument: Nowhere in the video description does it a) explicitly accuse the person of being the thief (so if he was found not guilty, the accused has no case there) and do so with malice or b) even make fun of the guy's dancing (which is a statement of opinion and wouldn't hold up in court).