The way facebook works is if their is if someone likes a page/topic and that page isn't yet in their cache then they send out the crawler to grab it.
The only way to stop that from happening would be to disable the facebook like button in the control panel, or possibly block their user agent, but that might prevent it from showing how many people like the topic.
As for google. They are always going to be there. But you can get more control of it and see what they are doing by signing up for their webmaster tools.
