People always forget that marriage is an archaic and largely outdated institution that has traditionally been about the acquisition and exchange of property and power between men. More so, women have been the tools of that transaction. Marriage existed solely to allow property to pass outside of a direct familial line. The idea of marriage for romantic love is a relatively new concept in mankind's history.
So as far as I'm concerned, "gold diggers" are doing marriage "right". In a society that still largely sees women as transactional property, gold diggers are simply playing the system to their advantage; utilizing traditional practices as leverage against slightly more progressive but still outdated ideals.
In 2013, women are still being told that finding a good husband who can provide for them should be at the top of their list of priorities, so why fault them for, you know, listening to you? Worse yet, there are still men who balk at the idea of a women who can or does provide for herself, and seek companionship out of desire rather than need. So, either we do away with the notion that women need to rely on men for financial security, or we stop being pissed when they rely on men for financial security. Can't have it both ways.