She's probably mounted on one of those vibrating benches with a dildo you can straddle. Howard Stern featured one once on his TV show.

It's a riding_machine. They were originally meant for passively exercising your core abdominal muscles.

See also:

• http://kotaku.com/5048857/suggestive-rodeo-riding-machine-shame
• http://www.sankakucomplex.com/tag/riding-machines/

Well this one clearly has an integrated vibrator, judging from Miku's face.

What you're referring to is a sybian.

Yes! That's the name for it!

I think Miku's enjoying it a little too much, though.

would fucked silly be a good tag for this one?

tactile_cacti said:
would fucked silly be a good tag for this one?

We aliased that to ahegao.

Miku being perverted nope nothing unusual here move along move along.