In an Email service on grammer and usage I receive from tipworld@boing.topica.com, came this discussion of spelling, which I paraphrase:

Unlike British and Canadian English, which double the last-letter consonant when adding a suffix to a root word which ends in a single consonant preceding a single vowel, US English usually bases consonant doubling on whether the last syllable is stressed in pronunciation. Thus, "traveled" and "bigoted," (accent on first syllable) but "repelled" and "allotted" (accent on second syllable). And, of course, plenty of exceptions.

Had anyone out there noticed the pattern? Why did it develop? Me, I've been blindly memorizing spellings or having to look them up. Duh.