This is why I always wear a name badge when I'm working on lots of different sites - I just b***y wish the people there would do the same. "Ian? Sorry, Chris? Where's Shaffaq's desk? Surjan? Surjit? Rajit! That's it, where's his desk? Oh, sorry, *her* desk?"
Last week I balls up migrating two users on a site called Ian. Not just Ian, but Ian surname-starting-with-L, so their user names were ian-randomnumbers-L-randomnumber. Luckily, Chris H, Chris H and Chris H were on seperate days.