"When typing in Japanese, your iPhone uses names and readings from your address book as a kind of second dictionary for its text auto-complete. This was a very smart way to program the iPhone since the most common reason to use non-standard kanji/words to begin with is because they're used that way in a proper name (which, if it's someone/someplace/somewhere you know, would probably be in your address book anyway)."
"not every iPhone application can "learn" words. Notes seems to be brain-dead in that regard. At the same time, using Safari's Google text entry field worked every time, expanding the database and adding new items to my keyboard dictionary. "