> However, nothing prevents the
> user from using any unicast address as an anycast address.
It is impossible even to say "someone uses an unicast as anycast."
Think a bit, anycast != unicast only from receiver viewpoint.
If receiver thinks that an address is anycast, it __ anycast.
> For e.g., I use anycast with IPv4 as a simple mechanism to provide
> failover between linux servers. You need to understand the constraints,
> but if you do, anycast is simpler, and more scalable than most of the
> other clustering schemes, not to mention free.
I am afraid, you say not about anycasts... Anycasts as defined in IPv6
(and can be used with IPv4 with the same success, provided ARP
liteners agree some simple requirements, borrowed from NDISC. Linux-2.2 does.)
are useless for any serious applications beyond scope of stateless
datagram services f.e. name services.
I am afraid you tell about _unicast_ assigned to multiple hosts.
This case has nothing common both with anycasts and with any
other practice ever approved by IETF to nowadays.