need some changed answer... Yes it will hurt your ranking. because google rank up also and give them marks, and if your shared ip has bad reputation it will effect.
see this thread Myth busting: virtual hosts vs. dedicated IP addresses. kinda makes me curious what this means "If your ISP does virtual hosting correctly, you’ll never see a difference between the two cases. We do see a small percentage of ISPs every month that misconfigure their virtual hosting, which might account for this persistent misperception–thanks for giving me the chance to dispel a myth!"
the only thing you must afraid of is your hosting company has offline your site for a long time. it happened to me when i was transfering my sites. dropped totaly
no problem at all! but be carefull with interlinking your sites which are all on the same IP. So don't excessive link the sites hosted on 1 IP. This is unnatural linking behavior.