Here Ill break it down for you big dick.
10-20 sites same host not smart but will probably go unnoticed if used as personnel blog networked (except if you use seohost, then your just boned)
5000+ sites same host = fail at everything
There is no logical way to rationalize this in anyways... Here are some examples...
Slow kid - "dude i thought google wouldn't know cause I took precautions to hide foot print"
Me- "5000+ same host"
Slow kid -"they have different ips man, well a few cause its the same host and saves some bucks.... No foot print man high pr!!"
Me- "5000+ from the same fucking host"
Slow kid- "Hey I made alot of money from you suckers with my blog network see you in the Bahamas bitches!!"