Is that what marketing is all about?
I think so.
Make promises and keep them.
Some organizations work very hard to weasel in the promises they make. They imply great customer service or amazing results or spectacular quality, but don't deliver. No, they didn't actually lie, but they came awfully close. The result: angry customers and negative word of mouth.
It's very easy to overpromise. Tempting to shade the truth a little bit, deliver a little bit less to save a few bucks. Who will notice?
The consumer notices.
If you need to overpromise to make the sale, don't bother. It's not worth it.
The best way to generate word of mouth is simple: overdeliver.