Cause Fires, get tangled in my..... errr where was I...
Any cable, properly selected, is rated to carry a particular current for its conditions of use. There are all sorts of regulations and calculations that, should, be done to ensure the wire is fit for purpose.
Ignoring isulation and other requirements. Having selected your bit of wire you also have to consider its mechanical properties. In particular minimum bend radius. This means that when the wire enters any fixed point it is adequately supported so that, under 'normal' use that minumum bend radius is not exceeded (under-exceeded?).
It also means that the overall insulation of the wire should be sufficient to support it such that, under normal use, the wire itself will not flex below the minimum bend radius for the conductors.
If you do not then the copper in the wire will work harden, become brittle and, eventually break. With stranded concuctors the failure is gradual. Individual strands will break over time leaving less and less conductor area intact to carry the design current. The result is that the wire will.... heat up at the point of failure.
That will be sufficient to melt insulation and in some cases the wire will behave like a miniature arc welder. Sparks are a possibility as well when, with movement, the frayed ends brush against each other.
Provision of that support or strain relief along the cable or at connector entry points should be inherent in the design and not rely on the end user having to dress the cable in any particular way or use additional methods to supply support. The most information the end user should have to be given is instructions about the minimum bend radius and not to exceed it.
I'd go as far as to be concerned about this 'magnasafe' concept. I don't know what it looks like but if, as I suspect, it involves simple 'flat' contacts with no positive positive mating/wiping of connector conductors the idea is bad in itself.
That might work for low current, <100mA, charging currents for low power battery operated devices, look at the charging connector on your mobile, but will run into problems for higher power, higher current devices. Going seriously technical if they limit themselves to 24V from the brick for the purposes of SELV, Safe Extra Low Voltage, requirements then for 100W you are looking at about 4A current draw..... not a 'good' idea.