One comment, the magnet for magsafe power supplies is actually in the laptop, not the plug.
Have you heard about people implanting a tiny magnet in their pinky finger? I think they've been mentioned on HN before... could give you insight about magnetic fields around you (assuming it was weak enough not to be a cause for concern itself).
EDIT: past story on the implants.
http://www.iamdann.com/2012/03/21/my-magnet-implant-body-mod...
Yeah, I've heard of the magnetic finger modification. I promptly was concerned about it, not quite sure why but favor caution; sure wouldn't want one given the possible consequences. Since earbud magnets are enough to warrant concern, I'll avoid what is likely more powerful.
Woolrich has a line of shirts I want which feature magnetic "button". Can't convince myself they wouldn't be a problem.
I had a pacer wire for about 5 days post-surgery. Shocked me once. That sucked.
Post implant, setup process caused several convulsions. Harmless, but gave me a giggling fit. Thanks to one wire too close to my diaphragm I couldn't sleep on my left side (compressed them together) for two years until they figured out how to reprogram it to stop making me twitch each beat.
Diagnostics is always amusing when they drop the heart rate to 40, and do it as if I won't notice.
One of the first warnings I got about having one was to not dangle earbuds around my neck where they would hang in front of my left shoulder. Other warnings about keeping distance from generators, magnets, shoulder-pressed cell phones, store theft-deterrent sensors, and even chainsaws (cardiologist & I got a kick out of wondering which would kill me first: the alternator's fields knocking out the pacer, or my passed-out fall into the still-spinning blade). MRIs...just don't even go there.
The problem with magnets is more complex than perhaps obvious. There's bad input, and then there's damage. What the girl is referring to is quite legitimate: defibrillators and pacemakers typically allow proximity of a magnet as a "master override" function. When I suffered an unrelated instance of atrial flutter (heart decided to run at 350bpm, pacemaker hit the brakes at 150...for 12 hours), the ER doc not having a diagnostic system handy forced the pacemaker to reduce to a much more humane rate by placing a good-sized magnet over the pacemaker; this allowed a more relaxed 2-hour wait for a technician to arrive and better diagnose & manage the problem (the subsequent drive-thru heart surgery is another story). She's raising awareness that sometimes this "master override" function can be induced improperly and even unknowingly, leaving the patient in a high-risk condition without knowing until periodic diagnostics or medical failure. A related issue she may tangentially raise awareness of is outright damage, with induced currents overstimulating the patient or frying the electronics (see aforementioned chainsaw issue).
She's raising a good issue. With the proliferation of tiny super-magnets, an enduring technical problem must be revisited: how to provide a low/no-impact way to essentially "hit the reset button" on an implanted medical device when there is no visible/external contacts? Not long ago, using a strong magnet to activate a magnetic switch was a sensible solution. Today, stronger magnetic fields are coming closer more often, risking activating a "safe/master mode", and there's not much way to alert anyone to the condition.
To address a few other points: Yes, any small but strong magnets like the magsafe plug are a possible problem. It's not an EMI problem so much as false input to a magnetic sensor. Defibrillators and pacemakers face the same basic problem, but the former moreso because the "master override" function needed is a function shutdown (need a way to turn it off and keep it off), while the latter responds in a more benign manner.
Glad to hear someone raising awareness of the issue. Amused that it's a child figuring it out and publicizing it. Thanks, kid!