Nice article on ars technica saying how you should use a blocklist or you will be tracked... 100% of the time if you're on P2P networks.
# If you don't use a blocklist, you will be tracked. Every one of the researchers' test clients that did not use a blocklist soon connected to an IP address found within those lists. It turns out that 12 to 17 percent of all IP addresses on the network belonged to these blocklisted ranges.