Often times in the official forums people will post a link to some WoWWiki article or something, and instead of the link actually going where it is advertized to go, it'll go to the Rick Roll video instead.
I personally am rather tired of always having to check the link to see if the video ends in uuiU, which seems to be the most common YouTube video used to Rick Roll people. There are some browser addons out there that'll stop you from being Rick Rolled, if you're so inclined to install them. But as always, be sure that you're getting these addons from a reputable source.
Have you been Rick Rolled lately? Share your tales of horror.