online video reveals personal information?

[Valmont]

I know people, especially women, do odd or extraverted things in front of a webcam, but most don't realize the extent it can have. They don't see past the simple act of doing it and often end up regretting it later. This being said, I don't think you should harass them about it and let them pray this video will never hurt them in any way. What you can do however is report the video to the site (Tumblr) and state you know these girls or that there is too much info that can help identify them and it should be removed.

Chances are the video won't spread so might as well leave it down. Report it and no more. If you see the video seems to be somehow popular, for exemple if it has tons of likes and regular visits on it's page, then you could warn them by sending them the link and saying something short like: "I think you should have this video of your B double O's Bs removed". That oughta do it.