The current installer doesn't permit installs without swap, choosing instead to pout and whine. Anaconda puts every partition labeled 0x82 into /etc/fstab as swap without even asking -- that'd be fine, except that's not really my preferred method of accessing Solaris/x86 partitions. If the user doesn't specify a swap partition but has enough disk space, anaconda should optionally create a swap file on the filesystem. Blindly mounting all 0x82 partitions as swap, though, is dangerous.
Adding to future feature requests that we will evaluate at a later time. Thank you for the suggestion.
The current beta release of Red Hat Linux (Roswell) will allow you to continue to install without any swap (although it will warn you appropriately).