OS X :: Running / Quitting Finder And IDefrag

One of the first things I did when I got my new MBP was to input the command that granted a 'quit' option for Finder, and since then, I've been keeping Finder quit / closed pretty much all the time. This is in part to free up what little RAM it uses (I know it's next to nothing, but it seems pointless to use even that to keep permanently open an application that's used less than 2% of the time) but mostly because I simply cannot stand keeping applications running if I'm not actively using them. Having tried to look this up, I've come across a wide variety of different thoughts on the subject, so I was hoping for something a little more clear-cut. I've read advice stating that Finder is just another app and that quitting it does no harm... and I've also read advice that insists it's part of the fundamental workings of the OS.... so what I'm hoping for is some kind of definitive answer as to whether it's likely to damage Snow Leopard at all if I continue to keep Finder quit / closed, or whether it really is necessary to keep it running the whole time?

Unrelated, but I'm hoping just as relevant to this forum as the other question... I have the demo version of iDefrag, simply to check the level of fragmentation on my files / free space, and I'm more than a little confused by the results it's showing. The 'statistics' tab show 0.1% fragmentation of files and 0.3% fragmentation of data forks (which is obviously insignificant), but the 'layout' tab shows well over half of my used space as red (which, according to the key, translates as 'fragmented'). The highest percentage of fragmentation on any part of my system, according to the 'statistics' tab, is in my free space, but even that's only at 1.8%, so wouldn't account for such a large chunk of neon red on the 'layout' tab, and certainly not one right in the middle of my used space.

So my question is whether there's a logical explanation for what seems to be two completely conflicting pieces of information, whether I'm just being an ex-Windows moron (I've only been a Mac user for a couple of weeks, so I'm still way at the bottom of the learning curve and very much still adapting to the differences), or whether there really is a conflict there that shouldn't be. Additionally, is there a means of doing something about that free space fragmentation without running a complete system defrag on the perfectly fine state of my files? I only ask because (though it's only 1.8% at the moment) what research I've done on the subject, while it makes the repeated point that Mac OS X defrags small files on its own, also seems to imply that it doesn't do anything to defrag free space, so I'm led to assume (possibly wrongly, but that's why I'm asking) that without third-party interference, that 1.8% isn't going to be defragmented on its own and will just end up getting bigger over time.