Paris is a very densly populated city. People are always surrounded by other people, and it is not rare in a restaurant or bar to have to share your table with a total stranger.
The Parisians will completly ignore you. This is often misunterpreted as being snob or snotty. For a Parisian, it is a mark of respect and politness. Privacy is very important, because there is so little of it...
On the other hand, if someone talks to you in a restaurant or bar, it means that he/she really means it!

