While cruising the new FAQ at TreoCentral, I noticed a seemingly bizarre answer to the question “My Treo 600's vibrate feature stopped working! Is there anything I can do?“  Apparently (and I haven't verified this, as my vibrate feature is working just fine, thank you very much) you have to simulate the vibration in a very specific fashion while the Treo is supposed to be vibrating.  I kid you not.

Every time you hear the alert, move your arm/hand/phone like you're knocking pretty hard on someone's front door, but instead of actually hitting anything, stop the movement suddenly in mid-air. Quit the movement when alert stops, resume when it starts again (or until vibrate motor starts moving again).

Um yeah, right. And if you're having this problem, you should read the whole post, as you apparently have to hold it in a certain way during the procedure.  And stand on one foot.