I love the fact that I can waste hours watching funny stuff on the net but I hate the fact that so much of it is fake. I don't mind fake stuff per se but it has to be done well (e.g. The Onion).
Some people think lies are inherently funny but they are wrong. There's nothing intrinsically funny about lying and there's certainly no comedic merit in convincing the victim of something that could easily be true. It's only funny if it achieves something additional such as including witty dialogue or making the victim believe an unlikely fact. For example, it's not funny to convince you that I'm a doctor but it might be funny to convince you that I'm a professional nipple tweaker.
Recently I read the story of a girl who prematurely got her new boyfriend's face tattooed on her arm. Turns out it was fake; a joke. Dammit, this is not humour. It's not funny because there's no good trick involved. There are plenty of nutcases that do this sort of thing for real - this entire scenario is (sadly) completely plausible.
The whole lonelygirl15 saga is another example of pointless, unfunny deception.
What annoys me most about this is that it detracts from the genuinely funny real-life stories. Failblog is a lot less amusing when you realise that any given entry is likely to be fake.
So, please stop with the lame pranks. Before creating your viral masterpiece, ask yourself: Is the prank difficult to pull off? Does it describe a highly unlikely event? Does it contain text or images that would still be funny even if the reader knows it's fake? If the answer is "none of the above", don't do it.