Re: Questions about populating RIR with customer information.

* Drew Weaver:

Up until recently, we were only providing the RIR database with information about our larger allocations /24 or larger. We have noticed however that many anti-spam organizations such as Spamhaus, and Fiveten will use the lack of information regarding an IP allocation as a blank check to blacklist entire /24s when they are really targeting a single /30 or a /29.

I don't know how this translates to actual blacklist entries, but for submitting complaints, blacklist operators ignore the smaller networks, whether they are in WHOIS or not. I would also expect that if you've got a significant spamming problem, some blacklists will try to entice *you* to do something about it proactively. Overblocking is often used for that purpose.