RFC 6177, IPv6 Address Assignment to End Sites, was published this week. It seeks to reverse the recommendation originally put forth in RFC 3177 regarding the assignment of /48 IPv6 prefixes to all end sites. The effort behind the RFC seems to have stemmed primarily from observations that assigning a "one-size-fits-all" prefix to medium-sized organizations and residential users alike is excessively wasteful in the case of the latter.
RFC 6177 has obsoleted its predecessor, updating or negating the three core recommendations as such:
1) It is no longer recommended that /128s be given out. While there may be some cases where assigning only a single address may be justified, a site, by definition, implies multiple subnets and multiple devices.
2) RFC 3177 specifically recommended using prefix lengths of /48, /64, and /128. Specifying a small number of fixed boundaries has raised concerns that implementations and operational practices might become "hard-coded" to recognize only those fixed boundaries (i.e., a return to "classful addressing"). The actual intention has always been that there be no hard-coded boundaries within addresses, and that Classless Inter-Domain Routing (CIDR) continues to apply to all bits of the routing prefixes.
3) This document moves away from the previous recommendation that a single default assignment size (e.g., a /48) makes sense for all end sites in the general case. End sites come in different shapes and sizes, and a one-size-fits-all approach is not necessary or appropriate.
In summary, the IETF has decided that deciding on prefix sizes for end sites is "an issue for the operational community." However, section five of the RFC does offer some guidance well wroth reading for those writing internal IPv6 address allocation policies.