That is so stupid (of them). It really irritates me too because people keep telling me what types of jobs to go for and then I read the descriptions and they say you have to be confident, bubbly and all the rest of it. I just hate that being quiet and shy are considered bad qualities. Maybe they are for some jobs but come on. The overall attitude employers have about it. ugh. Anyway, good for you, lol. =]
I personally don't really see a problem with the ad? As a receptionist you have to take a lot of calls, be very forthcoming and act confident over the phone. I don't see an issue with a company suggesting people who are more comfortable with this line of communication apply rather than those who would have a harder time constantly communicating with strangers all day long?
Yes the ad is over generalising, I realise that, but like most ads they try to be short, sweet and too the point. It's not a hard fast rule that if you are shy you cannot apply, they are simply suggesting that due to the line of work, being a shy person may not make it ultimately suitable for you.
If you want to do it though and feel you will do a good job SJ, go for it!!