With IPv4, it's pretty much a given that unless there is some specific need that warrants IP-based virtual hosting, name-based virtual hosting should be done to avoid needlessly exhausting the address space.
However, given that for IPv6 the current recommendation is that even home sites should receive multiple /64s worth of address space, is it not reasonable, absent operational practices in the specific situation which would make this difficult or prohibitive, to assign distinct IPv6 address to each web site, even when those web sites are co-hosted on the same server?
Assuming that a good address management infrastructure of some kind is in place such that one can handle the assignment of addresses, what might be good arguments for or against giving each web site its own IPv6 address?
For completeness, the relevant part of the above-referenced section from the RFC is (emphasis mine; note that this is for comparison only, and this quote does not make the question one about home networks):
At the same time, it might be tempting to give home sites a single /64, since that is already significantly more address space compared with today's IPv4 practice. However, this precludes the expectation that even home sites will grow to support multiple subnets going forward. Hence, it is strongly intended that even home sites be given multiple subnets worth of space, by default. Hence, this document still recommends giving home sites significantly more than a single /64, but does not recommend that every home site be given a /48 either.
Also for completeness: The relevant network does not yet have any IPv6 assignment, and I don't know the exact size of the assignment that might be made, but I'm hoping to get IPv6 set up and running within the next 6-12 months and would like to plan ahead a little to be ready when that happens.
Giving each website its own address makes it easier to see which website traffic is for on the network. This can help with accounting, attack detection and prevention and things like that. It may also make it easier to move a website to a different server because you can just move the address with it.
If you're not doing things like that the benefits are much less and the extra administration of IP addresses may get annoying. If you put dozens or hundreds of addresses on one interface it may impact performance on some operating systems, although I think these days the scalability is pretty good.