I started seeing 23s everywhere after I made a comment that I figured I'd be dead by 23 (of course, I'm currently 25 and still alive -- biologically-speaking, anyway -- but I still half-figure I'll kick off at 2323 military time on the 23rd day of the month on 23rd street or something and be buried in the 23rd lot, etc). I saw the number everywhere. My friend, rather big on Discordia at the time, eventually laughed and pointed out how 23 (as 2 + 3) was part of the `Law of Fives'. I read up on what RA Wilson and Burroughs had to say about the number, and it became sort of a running joke, but I was always only half-joking.
Then another friend of mine -- a fellow bluelighter, and a girl I presently live with -- she was mocking me one day and said that it was all bullshit and coincidence. She said it was just that I was looking for the number, that if she were to believe she'd see 444 everywhere, she'd start seeing it. And then she did... she saw the number everywhere, and she stopped laughing.
And for the record, I do think it's true that it's basically one's mind looking for the number, at least I usually like to think so. But damn it, I still get into those periods where I see 23s everywhere and I have to freak out and try and just laugh it off. When this comes along with more startling and meaningful coincidences, however -- such as with Burroughs `Captain Clark'-23 synchronicities -- you begin to wonder...
I've also got into periods where the 23 has been replaced by `8' and references to infinities and mobius strips, as well as 11:11, at which I always cried out `picket fences'. Whatever the cause, `tis kinda freaky.