Cell phone etiquette

Whenever I'm in a public restroom and someone in the stall is using their cellphone, I wonder to myself:

"What phone call is so important that you can't wait to leave the restroom to make?"

Then I think I should sit down in the next stall and make the loudest noises possible to make sure that the person on the other end of the phone knows that they are talking to someone who is sitting on the crapper.

I also think about whether or not the person on the other end is truly fooled and doesn't know that they are having a phone conversation with someone that is in a public restroom.

Do any of you have these same thoughts when you encounter this situation? Are any of you guilty of using your cell phone in a public restroom? Did anyone else in the restroom go out of their way to tip off the individual on the other end of the conversation?

Thanks for sharing your thoughts on this.