Charles King, in his TLS review, “Among the Circassians” (April 23, 2010, p. 11), of a couple of books about the Caucasus, writes that the North Caucasus is a region “that many Russians would just as well forget they owned.” This use of “just as well” took me aback—for me, it would have to be “just as soon”—but I suspect it’s a dialect difference, so I turn to the Varied Reader: are you familiar with this use of the phrase?
And speaking of just-based phrases, Noetica writes to tell me he has found an omission in the OED, of which he has informed them; to quote from his e-mail:
The meaning of “just in case” is given only at “case, n.1”, as a special application of “in case”:
 b. as conjunction (with sentence): in the event or contingency that, if it should prove or happen that, if. in case, esp. in just in case, orig. with aposiopesis, in case––, to indicate an unspecified apprehension of accident.
…Most importantly, nothing at “case, n.1” covers the sense of “just in case” at the entries with an asterisk, above. For example, this citation at “symmetric, a.”:
1979 K. J. DEVLIN Fund. Contemp. Set Theory i. 14 A binary relation on a set is an equivalence relation just in case it is reflective, symmetric, and transitive.
Here it means “if and only if”, or “iff” (see OED entry). The usage is common in philosophy (especially logic, and philosophy of language), linguistics, and mathematics. But it is utterly baffling to beginners.
I agree both that it is baffling when you first encounter it and that it should be in the OED, which I am sure it will. When Noetica speaks, lexicographers listen!