Do you remember Napster? They went all in on getting traction, succeeded, then got crushed by the music industry. Ignoring the law only works if you are bankrolled. Don't try this at home, kids.
Sean Parker is doing great. It worked out for him.
So the point stands. If you get serious traction, the worst that can happen is your current company goes under, years down the line, after you have cashed out and you then fail upwards into being a successful tech celebrity.
This is all a much better outcome than nobody caring about your product, as you "followed the rules", hampered yourself, and ended up with zero users.
Of course if you really piss off the wrong people, you'll get smeared and maybe even framed for more things than you actually did before being arrested.
Legal gray area. They could have waited years and years and tried to get laws passed to allow their business to function with a clean slate of legality, but bureaucrats would have never allowed it.
So is the point to try it if you've got Napster level success but not Megaupload level success?
And since there is no way to know which level of success you are going to achieve beforehand, the note of caution still makes sense I guess?