In Cecil’s recent article on PCP, at http://www.straightdope.com/columns/050325.html , the master writes:
Well, of course his publicist is going to deny it. It’s blatant poppycock. Everyone knows that buildings don’t have a 13th floor.
Funny… I live in Japan and every building with stories numbering 13 or greater do indeed have a 13th floor. The 4th floor, however, is often absent.
Don’t assume that all countries share the same superstitions.
The building in which I currently work has a 13th floor, as did both of the previous buildings where I worked.
I’ve never seen a building of 13 storeys or higher that didn’t have a 13th floor. I even worked on one.
The hotel was in London. I’ve worked on the 13th floor of a building, in London. They certainly exist.
I too have never seen an absent 13th floor. (Or rather, not seen one.) And it would be hard for people to claim to have survived from the 13th floor of the World Trade Centre if it didn’t exist.
Unless they’re in on it!
I jumped from a 13th story window, once, back in the 60’s…
My previous house was on a street which didn’t have a No.13.
We were No.11 and our neighbours were No.15.
Having worked in a Local Council in the past, I have to suggest that this may have been just because someone mucked up the count.
Mind you, the public are as bad 
I remember one person who wanted to name a new road “e-road Road”. Yes, e-road. Like e-mail, only er… not. They were incredibly miffed when the council turned down their suggestion. All for the best, I think, since it would almost certainly have lead to such things as Information Super Highway.