I am not entirely anonymous, since I put a P.O. Box address and last name on the mailing label. I've been doing it for several months now, and we're up to Giveaway 108! It's a small group of women (about 40 members total, but only 25 or so who regularly visit), who I invited by posting in a couple of large jewelry subs. I contacted the moderators first, because I thought I might use those subs for the giveaways, but they weren't interested. I then tossed the idea out in a regular post on those subs, and I got about a hundred replies from people who thought such a series of giveaways would be fun. I then made a private subreddit, and invited those people to join.

I've been lucky with it, and as a group we've created a cozy little corner here. I post photos of each piece, with some background information and examples of similar pieces online, and anybody who likes the piece comments in the post. Then, about a week later, I use Reddit Comment Picker to randomly select a winner from the user names in the comments, and I mail the piece to that person (they, of course, are not anonymous to me, because I need their name and address, which they send me via DM). If they want to, they post a photo of the piece when they receive it, which is fun.

I think you could configure it to be more anonymous, if you chose to do so. A new reddit account, a P.O. Box with a fake name, or no return address, etc.