OK then, go for it! But don't forget what is stated on one of the pages above, ".....but keep in mind that a power supply has a capacitor, and can hold a charge for quite a long time. I am talking on the order of 40 to 60 thousand volts here, so you really don't want to be the path to ground for it. Be very Very VERY omygodcall911 careful."
Having done so MANY times, and as there is a fairly good chance it will work, I say "spray away". (My preference is Gunk Liquid Wrench... not so aromatic). Aim your straw into the small open space between fan hub and its surrounding housing... couple of squirts, but don't drown it. Repeat several times, if necessary. If it "gums up", spray again. The spray will un-gum it. I have one rig that I had sprayed at least a dozen times over the first few months when it was new.... was going to take it in for warranty replacement if the spray didn't work, but it did. Over the last couple of years it's been just fine. Worst that's likely to happen is that you end up replacing the PS anyway. Spray attempt is free and takes no time.
I have found the best way to avoid the problem of a noisy fan is preventative maintenance. Many of us tend to leave our computers running around the clock, giving it lots of time to collect dust. Therefore I periodically take the computer to my shop and remove the cover and simply blow out all components (fan, power supply, boards, floppy drives, cd drives). One would be amazed how much dust a computer collects. However, if a power supply fan motor becomes excessively noisy, I replace it. No if, ands, or buts about it. The computer is to valuable a commodity to take any chances with. Some of these responses remind me of people that will pass by the local hardware store (2 blocks away) and drive 20 minutes to Lowes to save 15 cents on a furnace filter.
The guy who wrote that is an idiot. There are no voltages within two orders of magnitude of those numbers in a PC power supply. However, CRT flyback voltages do run into the tens of thousands. The capacitor in this case is the picture tube itself, and it can hold a charge for a very long time. Standard operating procedure is to use a large screwdriver to discharge the tube to chassis ground before doing any kind of work. I've been zapped by 14-inch monochrome tubes (many years ago); it wasn't much fun, and they only ran at about half the voltage of a modern 21-inch color CRT.
I'm an idiot? You are a fool, Diode. "Warning: the filter capacitors used in many switchmode power supplies can store an amount of energy that can kill - always discharge and confirm this before touching anything." http://www.repairfaq.org/REPAIR/F_smpsfaq.html#SMPSFAQ_014
Wally, The idiot I was referring to was the guy who wrote the article at http://www.2cooltek.com/case104_2.html, which you had quoted from. Not you. And my statement "There are no voltages within two orders of magnitude of those numbers in a PC power supply" is correct. The link you just posted mentioned "320 V or greater DC", which is indeed two orders of magnitude less than the "40 to 60 thousand volts" the original article erroneously gave.