We just got google slapped. We had just made it to page 1 for online drum lessons and then overnight we were pushed to page 3! There was a website that was hacked with a ton of porn related links pointing directly at our home page. It happened 2-3 weeks before the google slap. I can't see anything else that would have caused us to lose rank. You can check our links at backlinkwatchBor opensiteexplorer. The links were from njunitedmma and the webmaster deleted them relatively quickly so they are all 404s now.
I emailed him and he said they were hacked and all these links posted. I mean...what other purpose would there be for these garbage links and then we lose rank???