My basic question is why is the VSIZE for a 64 bit process so much larger than that of the exact same program compiled for 32 bit?

The following is the output of the /proc/<pid>/maps file for the 32 bit process.

00148000-00149000 r-xp 00000000 00:00 0               [vdso]
00149000-002d2000 r-xp 00000000 fd:02 8914142         /lib/libc-2.12.so
002d2000-002d3000 ---p 00189000 fd:02 8914142         /lib/libc-2.12.so
002d3000-002d5000 r--p 00189000 fd:02 8914142         /lib/libc-2.12.so
002d5000-002d6000 rw-p 0018b000 fd:02 8914142         /lib/libc-2.12.so
002d6000-002d9000 rw-p 00000000 00:00 0 
005c9000-005da000 r-xp 00000000 fd:02 17059392        /tmp/vsizetest/lib/libtesting.so
005da000-005db000 rw-p 00010000 fd:02 17059392        /tmp/vsizetest/lib/libtesting.so
005db000-0061b000 rw-p 00000000 00:00 0 
00661000-00689000 r-xp 00000000 fd:02 8917713         /lib/libm-2.12.so
00689000-0068a000 r--p 00027000 fd:02 8917713         /lib/libm-2.12.so
0068a000-0068b000 rw-p 00028000 fd:02 8917713         /lib/libm-2.12.so
00694000-006ab000 r-xp 00000000 fd:02 8917680         /lib/libpthread-2.12.so
006ab000-006ac000 r--p 00016000 fd:02 8917680         /lib/libpthread-2.12.so
006ac000-006ad000 rw-p 00017000 fd:02 8917680         /lib/libpthread-2.12.so
006ad000-006af000 rw-p 00000000 00:00 0 
006e5000-00703000 r-xp 00000000 fd:00 3150403         /lib/ld-2.12.so
00703000-00704000 r--p 0001d000 fd:00 3150403         /lib/ld-2.12.so
00704000-00705000 rw-p 0001e000 fd:00 3150403         /lib/ld-2.12.so
00983000-009a0000 r-xp 00000000 fd:02 8914997         /lib/libgcc_s-4.4.5-20110214.so.1
009a0000-009a1000 rw-p 0001d000 fd:02 8914997         /lib/libgcc_s-4.4.5-20110214.so.1
00ca5000-00d86000 r-xp 00000000 fd:02 6300601         /usr/lib/libstdc++.so.6.0.13
00d86000-00d8a000 r--p 000e0000 fd:02 6300601         /usr/lib/libstdc++.so.6.0.13
00d8a000-00d8c000 rw-p 000e4000 fd:02 6300601         /usr/lib/libstdc++.so.6.0.13
00d8c000-00d92000 rw-p 0
linux memory-management
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