Why block bots ?

Because of the time factor to fix. You dont want robots to index while your site is compromised with spam links like CssTricks or malware redirection like the Ford Wordpress site.

However I dont know, maybe blocking bots have the same negative effect on PR/SERP.

CSS Tricks spam hacking:
http://diggingintowordpress.com/2009...ection-hacked/

Having a spider grab your site while it's got spam links on it can be problematic. Blocking the spider temporarily is better in the long run. The spider doesn't have to know, especially if you send back some sort of transient error code to it, like a 503 error. Then it will basically ignore the result and spider you again later, hopefully after you've cleaned up the mess.

Yep, thats a good solution, Otto.

http://www.askapache.com/htaccess/50...available.html

I was going to publish the same information John did regarding CSS-Tricks and how their PageRank dropped suddenly after he realized the site was filled with Spam links.

Is it really getting to the point now where the same techniques I use on my desktop PC I need to translate to my blog? Like a AntiVirus program, spyware scanner, etc? Does anyone know of a post that has published performance results from WordPress sites with security plugins enabled? I think it'd be interesting. Specifically, speed/loading tests.

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I`m not aware of any performance tests, but I may do some light testing on one of my testing servers. What kind of data are you interested in ?

I guess loading times with the plugins enabled and disabled. Much like antivirus programs on the PC would slow things down, I wonder if the same thing happens with WordPress.

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I may some testing on sunday and PM you the results if you want to use it in an article.