> It has come to my attention in the course of moving the DNS for a number of domains that several of the ISPs in this country are mangling the TTLs on records queried by their recursive DNS servers. This behaviour seems to me to be undesirable in > situations where someone may have set a record to a shorter TTL to facilitate smoother movement between hosting providers. In the cases I�m seeing, records with TTLs of 14400 are being handed out with TTLs of 86400 by the service provider�s >servers.

If an ISP (or anyone) is breaking/changing TTL's (and maybe other stuff in DNS) on purpose I would think IMHO this is bad. Think would make DNSSEC signed zones fail + other stuff you have said as the ISP is playing around with it.

Maybe you don't want to name who you think is doing it but maybe if anyone is doing this they may want to comment on the reasoning behind it.