Some IXPs are not only infrastructure for interconnection and they sometimes offer some public services. I cannot determine all of them, but in example: NTP, traffic statistics, root DNS servers and some other (hope people from LINX or NETNOD should find some others).
i thought we had this discussion. those services should not be in the exchange mesh address space.
It was also discussed if the addresses should actually be announced. It was felt that this is not really necessary, but that some IXPs do it anyway. There was no conclusion if this should be part of the policy (e.g. the micro-allocation policy implemented in the ARIN region does require that the prefix is not announced). You have to announce addresses for "public" services.
see above randy