How do recessions affect friendships?

From Slate's new XX blog, here is Emily Bazelon:

Because of the downturn, friendships between two people whose Saturday night spending and overall class status used to calibrate precisely have now turned into trickier relationships between one person who still has money and one person who doesn’t. The sudden uneven footing isn’t easy to negotiate, as I’ve learned from the responses I got to my question about the effect of the recession on friendships.

Do income classes become more clannish in hard economic times?  There is either a very deliberate trade of favors for money, or you stick with those who can spend as you do.  An alternative model is that it becomes easier to ask what the other person can afford, and more gains from friendlly trade are opened up across a variety of income classes.