One of my websites was mistakenly excluded from crawling by a wrong entry in the robots.txt. When I noticed the drop in visits it was already too late. The search engines (Google, Yahoo, MSN, etc.) had removed the website already from their index.
I have changed the robots.txt immediately, but until now the website is not back in the index. I have checked in Googles Webmaster Tools and everything seems to be OK. I know it can take a while until you show up in the index, but from my experience it never takes that long.
Therefore I was wondering whether Google might have some penalty for websites which did not allow their bot to access the website. Maybe that it takes simply far longer until it can be reincluded? Did someone make the same experience? Any answers?