There are threads on Amazon and Kindle asking people to tag books, and be tagged in return. I confess I don't really understand tagging, but it seems to be a way of getting your books noticed by having tags in certain categories-- a useful system.
However, like many things, it can be misused. There is anger on the Historical Romance Forum tonight, because of the image that represents the forum. Previously, it was a well-known Lisa Kleypas book. Sometime around the beginning of August it switched to a CreateSpace/Kindle book by a relatively unknown author, which image was apparently being used to represent the forum because it had the most "historical romance" tags. To quote a reader on the board: "How could the book in the current image garner over 200 tags???? It's not a major author nor a well-known and widely-read historical romance. Makes you wonder, doesn't it?"
This set off a major effort by the forum members to get the Kleypas book back and to get rid of the indie book's image (which they have now accomplished). It also led to some bashing of the indie book and author, and some bashing of the tag system in general. I understand the impulse to use tags to get some free advertising. But this seems like a painfully blatant way to go about it. It's fine to use the tools Amazon gives you, but cheating in an obvious way does not win you readers, IMHO... and it tends to reflect badly on all indie authors, besides. Of course, for all I know it wasn't even orchestrated by the author, but by some of her fans. Either way, it doesn't seem to have impressed that group of readers favorably.