The “Blars” DNSBL (block.blars.org) appears to have gone on walkabout.
Created in 2002, the “Blars Block List” was an aggressive, semi-private blacklist run by a gentleman known to the greater internet community only by the pseudonym of “Blars.”
The "BlarsBL" had a broad criteria for listing. This included spam sending domains, open relays, sites with disagreeable spam reporting policies, sites lacking abuse addresses, those who host spammer dropboxes or websites, those who have threatened Blars or others with legal action, and sites originating break-in attempts and other exploits (open proxy, open relay, etc.).
The blacklist has been critizied for implying that payment was required for removal. From the site: "If you would like a site be added or removed from BlarsBL, you may hire Blars at his normal consulting rates (currently $250/hour, 2 hour minimum, $1000 deposit due in advance for non-established customers) to investigate your evidence about the site. If it is found that the entry was a mistake, no charge will be made and the entire deposit will be refunded."
Note: I confirmed today that all lookups against block.blars.org DSNBL will result in a match. This is the “Osirusoft solution,” also known as “blacklisting the whole world.” Intentional or not, this means that if you continue to use this blacklist, you will receive no incoming mail whatsoever.
If you are using this list to reject mail, I recommend you cease doing so immediately. It will block all of your inbound mail.
See this page at MXToolbox.com further confirmation of BLARS mysterious disappearance. This post from the newsgroup news.admin.net-abuse.email indicates that it has likely been out of operation since approximately December 18, 2006.