A Sphinn discussion thread led me to a post by Bill named Slow Down Nosy SEO's and Snooping Competitors.
In short, he gives techniques to "slow down" a competitor from analyzing your SEO techniques and just copying what you have done to benefit themselves. Now, I do not personally vouch for these techniques, that is up to you - but here they are:
- Do away with Archive.org and block them from archiving your site's changes
- NOARCHIVE your pages to block the search cache
- Block competitive analysis tools like Xenu
- Use private domain registration
- Block unauthorized bots and tools
- Cloak your pages to fool with your competitors
Again, I would not suggest all of these techniques. I am personally of the opinion to worry more about improving your own site as opposed to messing with your competitors minds - but that is up to you.
Forum discussion at Sphinn.