How Safe/Secure are Laptop locks?

You know the kind you plug into the little hole.
They use a little T that turns with the key to secure it. A little T shaped piece of metal...
ANyways my girlfriend has one, she was freaking out and wouldn't leave the hotel without locking her laptop to the leg on the counter, but she was too dumb to realise that you could lift the leg UP and slide the wire off...

When we got back, we unlocked the 6 locks on the door, and opened the curtain and was greeted by a great view of the opposite building's 36th floor, far away from any one that knows how to scale a skyscraper....

I looked at the lock and simply bent it a little, twisted, and pulled it...

But that's not the point, she bought some chinese lock before she came to the US and obviously got ripped. Sure if the would be theif is 2 years old it may work but....

I mean the laptop is generally plastic. Even if it is metal can't you just yank that thing off the table really hard and run away? I can't imagine it being too secure, even if it was a Tungsten Carbide lock the weak point is still the plastic laptop, that MIGHT have a re-enforcing bar... of brass...

 

I think most notebooks have some sort of a metal part surrounding the slot; even if hey don't, the slot will not break easily, at least not without ripping away a large chunk of plastic with it. But who would want a broken laptop ? unless the thief is after your data. A normal thief would not attempt to steal a laptop secured by a lock, especially in a public place (I think that is the idea).