The most worrisome part, to me, was that they then deleted several users' shelves (and sometimes also some of their reviews), notifying those users only after the deletions were finished. Goodreads later tried to explain their actions by saying the reviews they deleted weren't really reviews, but rather insults aimed at the authors. Even if that was the case, they could still have hidden the reviews and/or given the users who wrote them a couple days' warning before deleting them. As far as the shelves go, I've never had a "Badly Behaving Author" shelf of my own, but I can understand why others would want to have them. Those, too, could have been made private and were instead deleted without warning.
I have no current plans to delete my Goodreads account, since it's an incredibly useful way for me to keep track of the books I'd like to read. However, I'm on the fence about whether I still want to contribute reviews.
At least one of the people whose reviews I was following has left Goodreads and deleted her account. I'm currently exploring other options. Right now, the one I'm looking at most closely is BookLikes. It's really easy to import a Goodreads collection, although it takes forever - BookLikes has imported 16 of my books so far, with 764 more to go, and the estimated import time is 2009 hours. Also, imported reviews have all formatting removed - no paragraph breaks, no italics, no bolding, no links, and any Goodreads links you used morph into a mess.
I've only poked around on BookLikes a little so far. It looks like book-focused blogging, with a few social elements.
Another option I'm thinking of trying is The Reading Room. The main thing holding me back is that it appears to have a very small community - many of the books I've looked up have no reviews. I'm also thinking of giving LibraryThing another go, although, since free accounts are limited to 200 books, I'd have to pay to upload everything I've got.