It's more situational than anything else. My husband is in the military. He has 10 years in. He *loves* being in the military, and in 10-14 years, he will retire. The benefits are great and the salary more than adequate. He's very invested in his career...me, not so much. I'd had my dream job, and, after moving, nothing lived up to that, so, it was kind of disillusionary for me.
When DH retires, I can restart my career (I was a teacher) or go into a different field. We've even batted around the idea of HIM being the SAHP at that time before he transitions into the "civilian" work force. DD will be 12 if he retires at 20 years, 16 if he stays in until 24 - I think the teen years are probably the second most important time to have a SAHP after 0-3yrs, and I think it would be great to have my husband be that parent - if DD is anything like me personality-wise (um, so far, yes

) those would be some pretty heavy years of conflict between us (both stubborn and emotional, sometimes irrational), and it might even be *better* for DH to be the SAHP.

If we lost our freakin minds

and had another kid in 10 years (I'd be 41, so, not likely), I'd have no problem with him being the SAHP - although he'd probably want to wait until late toddler/pre-school age.
As for earning potential....had I stayed in teaching the past 3 years, I would be making (roughly) anywhere from 1/2-2/3 of what DH makes. Had DH gotten out of the army when I got pregnant, and I'd stayed teaching, we would have been closer to me making about 75-80% of what he made in '05. Not to mention, in this economy, some decent job security on his part. While it wasn't a factor in our choice, it's reassuring (I guess?) to know that it was also the correct financial decision.