(SNIP)
Currently, RIR's will issue an AS and will allow the issuance of a /24 to a multihomed enterprise, simply on the basis of being multihomed. From this point of view, it's easy to make the case that the proper "RIR-approved" boundary for prefix filtering should be at the /24 level. At any rate, Verio has been slowly liberalizing their filtering policy, and bring it into line with the rest of the industry.
If the RIR is issuing /24s, then they denote such on their minimum allocation lists, allowing providers to accept /24s from such blocks.
I think you may have misread my comment. ARIN ALLOWS the issuance of /24s to multihomed enterprises. The recent policy decision was made to allow upstreams to do this sort of allocation, without having to receive any other justification, other than multihomed status. This could seem to be RIR recognition of /24 as the globally routed "common denominator" - for those who insist on basing their filter policies on ARIN guidelines. :) It's often comforting to believe that there is a little more order than chaos on the internet, that there are standards or professional bodies out there to make law or proscribe best practice. However, this is simply not the case. ARIN and it's brethren are simply there to hand out numbers, not to provide a guideline on or even suggestion how to filter prefixes. Of course, we can all decide on our own, based on business imperatives, the best way to do that. I just hate to see people thinking that there is some sort of unspoken correlation between ARIN issuance guidelines and "best practice" filtering. - Dan