Guit by association and other random law type questions.

A few friends and I were debating a few thing at lunch and I was wondering if any of y'all know the answers.

Guit by association : What does this mean? Classic example, if I was waiting outside a bank and my friend robbed it without me knowing and I gave him a ride, would I get busted as an accomplice? Even if I was completley ignorant of what he was doing? That doesn't sound fair, but my friend said that in Texas I would be screwed. I don't know if guilt by association is what's its called, we just called it that during lunch.

Shoplifting What happens if I shoplift someting under $20. My friend is saying if someone shoplifts over $20 they go to jail, but under $20 they just get a ticket. $20 seems like an odd number, and kinda low.

Employer asking about convictions Can an employer ask if you have ever been arrested or charged of a felony? I thought they could only ask if you have ever been convicted. It might be dependant on the industry.