So, if the danger is so low, why does Apple recommend discharging the CRT? Simple: lawyers. If Apple didn't give this advice, and someone simply claimed injury from a shock, then they'd have a problem, regardless of the facts. Plus, if you get zapped, maybe you'll slice your hand on something in reaction. It's a simple act of CYA for Apple to recommend always discharging the CRT.
A reasonable case could actually be made for why you should advocate *not* discharging a CRT routinely. If you require that everyone do so, then you're asking that everyone deliberately expose him- or herself to high voltage. One slip of the ground clip, and you get the honor of being the discharge path. If you really believe HV to be so dangerous, does this sound like good advice? And if you do fear an implosion, then does it make sense to require everyone to scrape a tool under the anode cup, potentially scoring the glass and weakening it to the point of causing an implosion?
And even if a discharge itself causes no bodily harm, it sure can cause delicate components on the circuit board to fry, depending on the particular path the discharge current happens to take.
So, here's a perfectly rational, safe policy: If you don't have to work on the high voltage supply, keep your cotton-pickin' mitts off of the high voltage circuitry. All the components there are very well insulated. And of course, always work on the Mac with the ac power disconnected (not just switched off; pull out the cord). If you want to minimize the chance of getting an unpleasant jolt, just let the thing sit overnight.
