Most people I know would rather have saved the $100 and spent it on whatever they want to. Even if it's a guarantee that they will spend $100 on gas sooner rather than later.
I've thought about getting some ProV1's with my company logo and phone # stamped on them and giving out a sleve ($15) to my best clients.
Personally, I think $100 is a bit much. I think a personalized gift that cost less would mean more.