worthwhile debate

I suppose either one could be correct. I can't, personally, see any problem with either.

For what it is worth.

so i think it should be it's.

"okay im only gonna say this once... 'OHHHH if you being possisive then it's I-T-S, if it's a contraction then its I-T-apostrophe-S', scalawag"
Strongbad www.homestarrunner.com
(side note it's true)

Either. The only difference is the case you use. The worth is either in the predicate, or the worth is being possessed by "it". The "it" you are refering to is the comment that follows.

"For all it is worth." Predicate, worth it is.
"For all its worth." Possession, the worth of it.

Replace "it" with "the comment":

"For all the comment is worth." Predicate, the worth is the comment.
"For all the comment's worth." Possession, the worth of the comment.

Replace "it" with another pronoun, "they":

"For all they are worth." Predicate, the worth are they.
"For all their worth." Possession, the worth of them.

One last thing, in this particular example, you are using the phrase to show possession.

He rolled the R for all the worth of the R.

Emily, what about the alternative:

He rolled the R for all it is worth.

He rolled the dice for all their worth OR He rolled the dice for they're worth. Fitty-fitty.

Shit. Forgot the all.

Other alternative:

He rolled the R for all it was worth.

IT'S is a contraction of it is. ITS is the possessive form. You could go either way with this one because both make sense. .. for all it is worth. for all the worth that belongs to it. . . they both work.

cheers.

Either COULD work gramatically, but USUALLY, it's "All it's worth." For all that it is worth.