Why does many sites (youtube is good example) generate string of random number and letter instead of using for example the row id? 

usually its something likes this

```
bla?v=wli4l73Chc0

```

instead of like

```
bla?id=83934

```

Is it just to keep it short if you have many rows? Or is there other good things about this? Because i can imagine: bla?id=23934234234
dont look so nice

Thanks and cheers