Lawrence Lessig, founder of Creative Commons and professor at Stanford Law School, saw his site completely disappear from Google after some spammers managed to gain access to his site and inserted malicious code.
Lessig has cleaned the infected pages, filed a reconsideration request and his site should be back in Google soon but there are couple of points worth noting here:
1. Google Safe Browsing tool failed to detect any problems with Lessig’s blog.
2. Google can completely remove a website from their index if it gets hacked or found to be serving malware – earlier they were adding warning signs next to search results saying the site you are trying to visit may harm your computer.
3. Some website owners have complained that they lost their original organic rankings in Google after they cleaned up the hacked portions of their site.
Also see: Is Your Website Serving Malware