Is the argument that it added lots of erroneous Twitter posts? Get over it. You tweet when your eggs are too runny, a single tweet about a slideshow isn't gonna hurt.
Are you saying it makes the people who fell for the prank look stupid and unprofessional? You really think being the butt of a joke on April Fools Day is the end of the world for your public image? It's Twitter, not your company's quarterly report.
I, too, get tired of the endless barrage of April 1 jokes that flood my favorite sites once a year - its a little excessive, and in this case, not even that funny. But those that are calling for SlideShare's head in this situation either have too much time on their hands or need to stop taking themselves so seriously.
However, there is a subset of the social web that measures worth with simple numbers (wheter it be # of Twitter followers, FeedBurner subscribers, or SlideShare views). For the people who fell for it and are always talking about their big numbers, I would imagine that this could make them appear foolish, mostly because putting too much stock in those numbers is foolish in the first place.
I think it was a brilliant campaign. We are all talking about SlideShare and #bestofslideshare was a trending topic on twitter. I have a sense that the online slide sharing space is getting more competitive with new services launching, so why not use April 1 to help assert your position as the market leader.
Now that I know it was just a practical joke and not a technical blunder I still think it was unprofessional only now for different reasons.
* I don't believe this maxim, but a ton of people do. They are rich, I am not.
Facebook could delete everyone's profile and generate tons of publicity. They'd probably also go out of business.