Interesting to find this. I'm 50 years old and have been alphabetizing since I was about 12. It was an obsession from the period I was 12 to say when I was 18. I actually got headaches from alphabetizing everything that I thought, heard or saw. I got very good at it. I used to entertain my parents' friends at parties and actually performed at a school fundraiser. At the fundraiser people came up, paid a quarter (this was back in the 70s). They got a piece of paper and wrote down their word, then alphabetized the letters on the paper (taking them minutes to do) and then they'd try to stump me. If they stumped me they got a dollar back for their quarter. I made $58 for the school that night. I would literally alphabetize their word and say the letters within two seconds of their uttering it. It was a big hit. Once when I was a kid, Johnny Carson (for those too young check him out on wikipedia) had an alphabetizer on his show. My parents woke me up and we watched it. When Johnny gave the guy a word I alphabetized it twice as fast as his guest...crushed him...but Johnny's audience was amazed by the guy.
I haven't been obsessed by this for many, many years but I can still do it very fast when asked but not as lightning fast as I could when I was young. I guess I've lost a step as they say in sports.
My brand of alphabetizing has a twist. I can only do each letter once so if a word has two ns in it like say "perennial" (which has two es and two ns) then I see it as "aeilnpr" not "aeeilnnpr". It's the only way I can do it. I slow down to normal human speed if I have to say both es and both ns. Strange I know.
I've never sought a doctor's help or advice and, until now, never considered it part of OCD.I just Googled it for the first time today and found this forum. I just told my wife that I found this forum and people are linking alphabetizing to OCD and she said, "Gee, d'ya think?" So I guess I have an OCD and didn't even know it. It's OK, I have a pretty normal life and have a very good one thus far.I actually view it as a special talent.