Sunglasses as favors

I personally would advise against this. To me, sunglasses are a very personal item (similar to perfume), and a lot of them will end up getting left behind. If you are set on having favors, might I recommend doing something edible? In my experience, those are the only favors that don't end up getting left behind at weddings.

I agree. Most everyone I know wears prescription sunglasses, so I wouldn't wear inexpensive favor sunglasses (unless it was for a quick picture or something). If your wedding will be outside at a time when people are going to need sunglasses, I'd guess most people would bring their own. (However, we live in So Cal and everyone has/wears sunglasses on a daily basis, so that might be a regional thing.) Especially sunglasses with a wedding personalization would be a favor I'd leave behind or throw away immediately after the wedding. Favors definitely aren't necessary, but if you want to do something, I agree with pp about something edible. Daughter & SIL had 2 large chocolate chip cookies in a bag with a cute "Thank you for sharing our day!" sticker and none were left at the end of the night.

I, as a guest, wouldn't take them. Everyone has a different style and such, so it probably wouldn't cater to most of their liking. I could see kids playing with them, but I don't see most adults wearing them...especially if they say someone else's wedding information on them. I'd suggest edibles if you really want to do favors (cookies, candy in small bags, brownies, suckers, etc) whatever may go with your theme.

I've seen bulk ones on Amazon! I'd also check stores like the Dollar Tree

Here in California, everyone has their own sunglasses already, so this would not be a good favor for us.

I've seen personalized fans, which are always good to have in a warm climate. Flip flops are cool, simply because there aren't as many "style" issues.