Because anyone in the skypehaus is allowed to add anybody, even members who don't actually exist, people have been known to add fake members. A lot.
Most Notable (the ones we even remember) Edit
-raohorse and raopig
The Valtteri Incident Edit
Once upon a time, user Horikawa Otane tried to add "valtteri" as a fake, but it turns out there was actually a user with the account name "valtteri". We noticed this when there was a space in the name "Valtteri Korhonen", and you cannot /add with a space in, since skype would then count it as 2 users.
Since, however, the REAL Valtteri has been added. Let's uh… hope that goes well.