You know what drives me crazy about ARCs? There were a good number of ARCs distributed of my book. Only a very tiny number of people actually read and reviewed the book, consequently there was very little buzz about it before it came out, and I suspect the lack of enthusiasm influenced certain factors around the release.
Now, several months post-release, a few people who have been sitting on this ARC for over a year have heard that the book is good, and they have announced that maybe, just maybe, they might read the ARC, after all... You know, because they didn't before. It didn't interest them in the least, even though they were glad to grab copies for themselves when they were being given away at conferences (intended for booksellers and librarians).
So, to sum up, these people just had the book sitting on their shelves, unread by anyone, and they're only now giving the ARC (not the real book) a shot because it's getting good word of mouth. This ARC could have been grabbed by a bookseller, by a blogger, by anyone who would actually read the thing. I don't care, even, if someone grabbed the ARC, tried to read it, hated it, stopped at page ten, and then posted a blistering review-- at least that person TRIED to read it, which is the reason ARCs exist. To be read. NOT to be hoarded so someone can get a thrill at the sight of a huge number of unreleased books sitting on her bookshelf.
The whole hoarding of ARCs pisses me off more than people selling it on ebay (because at least a reader buys it), or people immediately giving it away on their blogs without reading to drum up traffic (because again, people who get it in the giveaway are likely to at least try to read it!), or even people pirating it (because at least people who pirate it actually READ it, and they don't cost my publisher the expense for the ARC). When you grab an ARC you have no intention of even reading, and just squirrel it away from everyone else, then you are actively screwing me over.
I feel strongly about this because sometimes I even get tweets telling me they're going to read my ARC now that the got at event X over a year ago. How am I supposed to respond? Great. So you didn't buy a copy, you sat on a promotional item that never got to fulfill its purpose, and you're only reading because other people who actually did read told you it was worth checking out... Am I supposed to be grateful?