Sock knitters all over have had a dilemma for as long as socks have been knitted-most everyone has two feet, and they could only knit one sock at a time, which could get tedious. Then along came circular needles, which allowed women or men to knit a pair of socks at the same time. Then some enterprising person figured out how to do a pair of socks on one very long circular needle.
Now-what if you didn't like using circular needles to do socks (or other small circumference items)? What if you preferred using double pointed needles-how would you knit two pairs at the same time then? There are two options-both of which I've either done, or am trying.
The first method is to use two sets of DPNs-one set for each sock-then work part way on one sock, switch to the other and work the same amount on it. This works pretty well-you don't exactly do the pair at the same time-you're simply working on one, putting it down and working on the other.
The other method-which I've already linked to in a previous post or two-is to use one set of DPNs and double knit the pair of socks. Double knitting has been around for centuries-usually used to create a double thick fabric such as a nice warm baby blanket. However, you don't want to tie your two socks together-you want to keep each sock separate-so you have to be a little more diligent about watching your yarn so that you use the right end for the right sock.
Anyway-I said all this because a couple of people pretty much dismissed the technique as grandstanding and didn't see the point. The point is-if you can't get the hang of circulars-or you just don't like them as well-this is a perfectly valid method to knit a pair of socks. The author even said you could do it with circulars as well-whether using two or one long one. Now, I really don't see the point of double knitting socks on circulars since there's plenty of room on them to keep them separate, but for DPNs, it gives the DPN lover a way to knit a pair of socks-if she/he's patient enough to learn the technique. About the only thing I wouldn't recommend would be trying to DK socks with cables. Lacy patterns may be possible with a bit of finageling, but I'm pretty sure cable socks would be much too tedious and stressful to try DKing-try the other method instead. Actually-all in all-for anything other than a basic knitted sock, I would knit them one at a time or do the two socks on two circs or Magic Loop-DKing would work best for just your basic stockinette stitch sock with K1, P1 ribbing.
An aside: The 'cheat' method of casting on, to me, works much better than the cable cast-on she uses. But in that YMMV. Either way-the cast-on and first round or two will always be the most tedious-whether DKing or not. After that-you pretty much sail through it.
I may change my mind once I reach the heel-who knows? All I do know is, so far, I like this method and it's fun-which is what knitting should be. I do recommend taking frequent breaks from it until you're comfortable with it-that way you're less likely to accidentally cross your stitches. Simply pick up something mindless to work on to clear your mind, and pretty soon DKing will be almost as mindless as a st st dishcloth-except you'll have to watch your yarns more closely. I'm comfortable enough with it that I simply join and start the first round in my ribbing pattern-usually K1, P1-instead of knitting the first round.