LOGNAME_MAX should be increased to 32
The current username length limit of 8 is extremely restrictive and will hopefully change in the future. To ease a future transition, applications using the LOGNAME_MAX constant to determine buffer sizes should be migrated to the dynamic value returned by sysconf(_SC_LOGIN_NAME_MAX). A quick search shows there are still several such consumers in ON.
(See discussion on long user names for PSARC/2010/184 here: http://arc.opensolaris.org/caselog/PSARC/2010/184/mail or here http://mail.opensolaris.org/pipermail/opensolaris-arc/2010-May/thread.html#21475 )