Cosmetics/hygiene products, not so much. I'm much more of a "try it out and see how it works for me/my body first" kind of person.
For restaurants though, I always go on yelp but that's because as a celiac, I need to know how allergy-friendly the place actually is. With gluten-free food becoming more of a fad, a lot of restaurants claim to have a menu or claim they can accommodate, but don't do anything to avoid the allergen. For example, I've been to a place where the fries were listed as a gluten free side, but the waitress informed me that they were cooked in the same oil as the other fried foods made with wheat flour. So, even though they claim it's gluten free, it's not.
I need to avoid situations like that because while I love going out to eat, I will be down for a week if I ingest any. So I like to do some heavy research before trying out a new place. It's exhausting ;P I actually think I'd use yelp a whole lot less if I didn't have this problem.