For pranks, I prefer when they're mutually enjoyable.
A great example of this is the "Photoshop Live" prank by Erik Johansson, in 2013.
He basically took pictures of random folks waiting at a bus stop, and live-photoshopped them into funny scenarios, being displayed on a screen in the bus stop.
Good, clean fun for both parties.
As for vlogs, I rarely watch any, but I prefer when they actually have substance, like updates, happenings, or basically, just stuff that I wouldn't see a dozen times a week in my own life. Interesting stuff.