If you are are working in a ribbing pattern (and there are many versions of ribbing, and you think its stretchy enough, you can bind off in pattern (no special 1 x 1 or 2 x 2 at the tip.
to bind off, i would:
switch to simple double knitting, (*k1, bring yarn forward as if to purl, sl1 bring yarn back, )
worked in the round, there is a slight change.
on R2, you slip 1 (yarn back as if knitting, not purling! and then yarn forward and P1, (not knit 1)
it take 2 rounds to 'work" (vs slip) each stitch, so do at least 4 'rounds
(2 rounds of K1, slip1, alternated by 2 rounds of S1, P1)
then bind off by grafting knits to purls.
(if that is too complicated, after the 4 rounds, 'seperate the knits and purls (use a spare circ, or another set of DPN-they can be smaller (it won't matter, and with the stitches seperated onto double needles (outside set holds all "knits" inside set holds all "purls' graft. (again graft knits to purls, only now, on 2 needles, its a bit easier to see the process.
(you don't have to seperate all the stitches, if working on 4 DPN's, you can seperate and bind off 1 needle at a time, (and just slip last stitch on a needle to next as work. )
Margarget Radcliffes' new little book on Knitting techniques covers this sort of grafting, (and so the the TechKnitter blog http://techknitting.blogspot.com/
) (and many others, Rig book of knitting, yada, yada.
this is a tubular bind off, and the 2 rows of 'stocking knit (that what it ends up looking like) look fine as an edge.
or you could just do a standard bind off in ribbing,(knit the knits, and purl the purls as you bind off.
(i love the tubular bind off for socks (and the oppsite tubular cast on for cuff down socks) i think the edge is both neat and stretchy!)