molgrips... not every file system needs defragging...
If by "need defragging" you mean "suffers from fragmentation," I challenge you to name one that's in widespread modern usage.
FAT - ostensibly introduced fragmentation to the masses.
NTFS - initially claimed not to need defragging by MS when it was introduced, they later said 'oops' and backpedalled. Has real-time optimisation to keep fragmentation down but still gets fragmented.
HFS+ - like NTFS, attempts to keep fragmentation to a minimum on the fly but can still get fragmented.
ext2 - needs defragging.
ext3 - can't be defragged natively (well, without converting back to ext2) but still fragments over time.
ext4 - recognises issues with ext3, proposes to re-introduce defrag.
"Can't be defragged" isn't the same as "doesn't need defragging." However, if when you say "need" you're arguing that fragmentation isn't a massive performance issue on a modern machine except in certain very specific circumstances, be that on Windows, Linux or OSX, I'd agree with you. It's largely a non-issue.
If as I suspect it's merely a badly researched attempt at willy-waving that "the Mac doesn't need defragging and PCs do," modern Windows OSes run a weekly scheduled defrag task on a very low system priority in order to keep fragmentation to a minimum. Most people aren't even aware of this and it can of course be disabled. The Mac, however, doesn't do this; not because it's not required but because it's not possible.
To defrag a Mac requires third party tools (not free) and requires exclusive access to the volume whist it runs - so you can't use your computer. It's also inherently risky, something Microsoft managed to fix back in the 90's.
This is fun, anyone else want to make any wildly inaccurate claims to the supremacy of their platform or have I made my point? (-: Hey I know, shall we do viruses next?
Since when did I say I use a Mac?
"Need" in this context is from a performance perspective, not a technical statement saying it cannot be defragged. So bringing fragmentation into the Mac Vs. PC arguement is pretty pointless, as it brings very little noticable benefits for the average Joe Bloggs desktop.
Now who's waving their little friend around by listing filesystems?