> The vast majority of applications do not pick their source address, nor is > there a compelling reason for them to do so. not in IPv4. if IPv6 has site locals more applications will need to do so. > A large number of applications > don't even handle multiple destination addresses properly, so expecting this > additional intelligence for the source address is irrational. again, you're trying to extrapolate from ipv4 experience to ipv6, but such experience isn't necessarily a good indicator when ipv6 presents a more challenging environment than ipv4. then again, if dealing with multiple addresses for a host was hard in ipv4, it's not going to be easier in ipv6.