Sandra Bullock is suing a watchmaker for using her name in ads without permission.

Using a celebritiy’s name (or even a photo) without permission for commercial purposes can lead to a serious lawsuit, especially as many celebrities live in California and California law provides for robust protection of the Right of Publicity.

But even non-celebrities can sue under their right to privacy if you use their face or name without permission in your own movie.

Generally, you should always get a release from anyone you videotape or film.  Also, have your script vetted by an entertainment attorney before you shoot!  And save yourself some trouble.