DroneBL administrator here! DroneBL does list many classes of abusive IPs, although most of our listings originate from IRC (as opposed to, say, Project Honeypot, which sources them from web spam). That said, though, it's apparently very popular to abuse IRC with open proxies, "free" VPNs, and many other sources of rotatable IPs, most of which overlap with what website administrators deal with. I am aware of a few sites that use DroneBL to measurably reduce abuse.

Note, however, that you may find our listing coverage lacking for web-only issues, such as WordPress pingback spammers, forum spammers (not using a proxy or VPN), etc. Especially in comparison to something like Project Honeypot.

A layered defense is the best defense. Firewalling, application hardening, rate-limits, hellbans, risk-scoring, etc., especially in combination with a blacklist, can significantly frustrate and discourage attackers and spammers. No single measure (other than extensive manual moderation queues) will prevent abuse entirely, but the more roadblocks you put up, the more likely the abuser is to give up.