Laptops and power plugs

The most common problem with laptops (aside from Windows issues) is the power plug, aka power jack or AC adapter.
Because laptops have to be made to exacting specifications, there is little to no room to reinforce the AC adapters position on the motherboard. This means that the rougher the user is on the equipment, the sooner the plug will be worked off of its mounting.
If a person is continually jamming the plug in or, more commonly, yanking out the cord then the more likely they are to pull the adapter off of its mountings.

How easy is this to repair? That depends on the make and model of the laptop; some brands are far easier to disassemble and reassemble than others. Also, it depends on the extent of the damage.
If the problem is found when the plug is "a little wiggly," then its a relatively quick fix because the mounting points can be reset and reinforced.
If the first time the problem is noticed is when the user notices a "strange rattle where the power plug was," then it is probably too late and its time for a new laptop.

The bottom line is: be gentle with your power cord, and it will outlast you.