you guys are funny! Looks like HostPC is blocking pings, which is acceptable, I do the same thing with all my servers. Major sites like Yahoo etc. usually services such as Akamai etc, so they don't control the policies in place.
yes and no, the firewall still has to process (drop) the packets, but the system will appear to be 'invisible' to regular script kiddies, so they usually will move on to the next target. It also makes OS fingerprinting a 'tad' harder.