PS/2 cant always be used as it has been dropped by all the big-name manufacturers although many motherboards still have PS/2 ports.
Speaking of incorrect.... 
The same folks predicting the demise of the PS/2 connector "in a couple of years" made that same prediction almost 5 years ago. I argued with them then, and I'll do it again now. It's still present on far more motherboards being manufactured currently than not. One needs only to go to the major manufacturers and look at their current offerings. I went o the first "big-name" manufacturer that popped in my head (ASUS) and it's quite obvious that they have absolutely not "dropped" PS/2. Even the current "Mini-ITX" boards from VIA still have the connectors, because those boards, unlike their other smaller offerings, have room for them.
It's still there because consumers expect it to be there, and it doesn't cost the manufacturers much to include it. Most of the systems you will find out there that don't have a PS/2 connection are designed specifically for very low cost, or very small form factor. Anyone who claims they know when the PS/2 connector is going away is at best, speculating and at worst, deliberately attempting to mislead.
If you have a PS/2 port on your system (and you probably do) and you aren't using it, it's an excellent, and trouble-free connection point for your arcade controls.
RandyT
This time it is different. We are about to say goodbye to the ATX mobo-form factor for >80% of all desktops, and consider most computers sold are notebooks! Who buys a seperate mobo nowadays? Small is the new form factor, and that kills space for a PS2 port. Especially when there is a new battle between HDMI/DP/DVI that needs a playing field on the port-bay somewhere!
Intel does not get it right now with this crap. Where is DVI? What is that GODZILLA PORT doing there? It looks like a MAC PLUS FLOPPY PORT. What TF is GMA 950, my Commodore 64 had more graphics power! Looking at the mounting holes, I guess you are supposed to put it in a huge tower either with the giant void filled with concrete to make it "dead" silent, with the giant void as hamster cage with a running wheel to cool the Atom or to accommodate a
12 disk floppy raid. That GODZILLA port is a custom 12 channel USB raid port after all! Although I have to say 60 euros for almost a new computer is pretty much ok.


Asus packs the same chipset a lot better:

This EEE box is amazing. It can replace 90% of all business desktops and is a whopping 220 euro including a Windows licence! BTW, do you see the PS2 port on that?
But Nvidia gives us an idea, more compact than a flopyy drive was in 1984!, of what a PC will be like next year (one of the big toasting-iron makers goes for low-power video chips now!):

This years atom is still a slouch, but the 2011 one baked on 32nm is like a good core2quad today! If the videocard makers manage to create a compact PCI-X variation and to get real 3D power back under 20 watt or so, our kids won't get the concept of a miditower anymore.
Résumé: in 2011 the desktop looks like an EEE-box, has the power of a Q9550 and the videopower of a 8800GT, uses 30 watts, costs 200 bucks, still has no Blu-Ray and definitely has NO PS2 port and YOU would be stupid to put anything else in a MAME box! The cut power bill moving here from that old P4 you put in today makes it earn itself back within 2 years of moderate use.