I might be going a little off topic - but this thread got me thinking... There are many reasons for partitioning a hard disk. Most notably, because it can make organizing your files that much easier. That said, I personally am weary of partitioning having learnt the hard way that the virtue can become the vice. Please let me explain.
Partitioning is often seen as a good idea. By partitioning your hard drive into clearly defined sections, it makes it easier for you to logically organize your data. (For instance, one for system files, one for applications, one for music files, etc...) And having one's relevant data all neatly organized on a particular partition may make the task of being (and staying) organized much easier. Should the partition where an application is installed become corrupted or accidently deleted, the data in another partition won't be erased. You will only need to recover that one partition, which is certainly faster then recovering the entire hard disk. Partitioning can help to increase security without hampering performance. (For instance, you could choose to encrypt only those partitions that need protection, while other parts of your system run unencrypted and hence faster.) Hard drive partitioning can help your computer find data faster. (For the computer needs only to search one partition, and not the whole disk.) And should you wish to have another OS system installed (ie; Mac OS 9.2 or a previous version of Mac OS X), partitioning allows you to do so without having to physically install another hard drive...
However, there can be some drawbacks...
Mac OS X requires a certain amount of free/empty space available in order operate at maximum efficiency. This amount is generally much (much) more than you or I imagine. In fact, it isn't uncommon for "temporary files" to exceed 500Mb in size. Point being, that partitioning can decrease system performance if you haven't left it enough space to play with.
Applications often install program code into the OS system itself. If you have placed your applications on a separate partition, you may find your hard disk's heads are forever having to move back and forth between the two partitions. This, obviously decreases system performance, not to mention wear and tear on the hard drive itself. (And for this reason alone, I can understand why a hard drive manufacturer might be advising against partitioning.)
Should the disk fail... guess what? You don't just lose the affected partition, you lose them all! And from personal experience, I have found that it's much harder to restore and re-mount a damaged partitioned drive than one that isn't.
And lastly, with many partitions it is very easy to double up on data. Applications tend to automatically save to the last place a file was saved to. So extra care needs to be taken to specify the correct partition. And should you save to the "desktop" - it's not enough to just move the file to the relevant partition - oh no. You will also need to delete the original file. Because moving it, will only copy the file from the boot partition to the partition you move it to.
I mean, if you're really into organizing... How hard is it to keep them in relevant named folders? Or even better, (don't be cheap) buy another hard drive. At least you might also gain a performance increase...
Just things to consider...