There's a number of strange things going on here -- as far as we know, this isn't an official Blizzard move, but most of the people spamming ads in the game are shady gold-selling websites, not real corporations with bigger profiles. And the weirdest thing might be this: Eharmony on Arthas isn't a one-time character created to spam in Trade -- he's level 80 with 450 Jewelcrafting and Mining. There's actually a lot of characters with the same name around, with different levels and classes, even in different guilds (though this one is probably the funniest).
Very weird. At the very least, the spammer's aiming to lose his character, and at worst, if this is an organized action, Blizzard might actually have a case against eHarmony for spamming inside the game. Have you seen any other ads like this around the game?
Update: Mystery seems to be solved: it was just some guy messing around. Strange way to mess around, though. He's in our comments, and says he's getting a free name change after the GMs said what he was doing was not so cool.