As the number one transit etiquette blog in the Bay Area (note: unverified), we feel it is in our duty to bring you the latest news in public transportation behavior. In the past, we've brought you fights on busses and fights with streetcars. Here now, a little love on public transit, as one amorous couple was recently filmed apparently grinding their way through the Transbay Tube.

The video, which would probably be rated R by the MPAA but is still not something you'd want your boss checking out over your shoulder, was posted to Facebook for all to see yesterday and, judging by the title, was filmed last night around 10 p.m. [Update: someone on Twitter claims it was filmed months ago, but we have no way to verify that.] There's not a whole lot of nudity here, but it seems pretty obvious what's going on. We already knew the BART seats were gross, but watching these two go at it will totally change your perception of all BART seating forever. You've been warned:

There it is. Now that is something you will have to live with every time you ride BART. "Do you think someone had sex on that seat?" You'll wonder to yourself before sitting down anyway.

The video racked up almost 700 Facebook likes and 750 shares as of this writing, and it's amazing not a single person has flagged the video yet. (And if it does get taken down, don't be surprised when it shows up on World Star Hip-Hop.)

The video's Facebook comments covered a range of topics:

• Sanitary conditions: "That's nasty"
  
• The girl's mental state: "That hoe must be on crack only crack heads do shit like that smmfh"
  
• Political commentary: "I guess this was the cum stain that made the workers go on strike."
  
• Defending the rights of consenting adults:"Eh, who cares? As long as they are two consenting adults, there's not a gaggle of school children near by, and they're not getting dick and pussy juice all over the place. Besides, worse things have been dribbled and wiped on those seats."

As our colleagues in New York wondered when subway blowjob videos hit the internet, who's rudest here? The people having sex on BART or the guy filming people having sex on BART and then posting it on the Internet? Better question: is BART taking over the New York subway's title of most naked transit system?

Update, 6 p.m.: Well that was quick. The video was taken down from Facebook. We've already replaced the video with a version from World Star Hip Hop, which is less scrupulous about these things.

[H/T: Mission Mission]