When I sell something I leave an option for people to send a testimonial. When they send me one, am I automatically just allowed to use it? (obviously they sent me it knowing I wanted to use it I said so) I'm just not sure how that works.
I would think that if you put in some sort of disclaimer saying something to the effect of "any portion of your testimonial can be used on our site....blah blah blah" would be enough to cover you. But even that probably isn't required.
As long as you say that you are looking for testimonials you should be fine. If you tell them that is what it is for they should be smart enough to know that you want to use it on your website.