I also agree with gravehearted to be cautious, especially since with many things like this you will find conflicting information. Some say it's fine, some say it isn't.
http://www.medirabbit.com/EN/Food/Food_main.htm Click on topic that says "TOXIC TO RABBITS" and it brings up a PDF file that shows garlic in the toxic category.
I've also included a PDF attachment from the ASPCA Poison Control - you'll need to scroll down to see the information about garlic. It includes cats and dogs with small animals reactions
With many things it's like this - for example: like salt blocks and mineral blocks you will find sites that will encourage their use. But unless there is some illness that requires a rabbit to need more minerals or salt, then it is not recommended by the majority of the rabbit experts. Now, of course, that is just an example. But what I am trying to say is make sure to know both sides - with garlic it might be just a dosage issue. I have no idea and so that's why this thread encourages me to learn me. (I love learning new stuff!!)
I am definitely for anything that promotes a healthy life for our bunnies but I need to educate myself more than just of couple of articles for each side. I'll make some calls to to a few experts and consult with my vet. She's very open to herbal remedies and has recommended them to me before, and the one time I asked her questions about certain plants and herbs that she didn't know about, she researched and got back to me.
I also asked this question on Etherbun, as they are more medically oriented. Though I know I can get conflicting info there too.
So I'll continue to research, and in the meantime, in my opinion, if I were you, I would still keep them but just wait for more information before I offered anymore.
I'll keep you updated and if you find out anymore info, good or bad, just post it to add to the research.