As a counterpoint, a friend of mine was knocked by when she volunteered for a local charity. "What qualifications do you have?"
The question sounds elitist, but the point was that charities often have metric shitloads of untrained helping hands. What they need, right now, is people that know how to manage, run finances, computer networking. Advanced skillsets.
I actually think the 'earning to give' mindset would really just end up as more consciential salve rather than a new way of thinking, much like people already do with minor donations. "Working on Wall St" changes the way you think. Case in point: another friend of mine was in a relationship with a hardcore Anarchist for 5 years, and came from a poorish middle-class background herself. She'd worked shitty working class jobs. She was pretty exposed to the plight of the poor and aware of poverty issues. Then she got a job in banking. A year later she got a raise of $10k, and she was negative about it, bitching about "the government taking half in tax" and it going to "useless welfare". Complaining that despite her tax load (seriously, got a raise, and all she could do was complain), she still had to help out her single-mother sister with money. Welfare was worthless, why should she have to pay so much tax? She got a bit of a shock when I said "So... what about all those other women like your sister who don't have a sister in banking?".
And here in our software bubble, I have a friend who earns 50% more than the national average household income (average, not median). He talks as if he's poor - and I see similar when I read conversations here on HN. It's awfully common for a software developer to see someone else doing the same thing and making a few dollars more, to then reclassify themselves as 'poor'.
The point is that where you work and who you associate with change who you are and how you behave - and, ultimately, have a good chance of removing people from the pool of 'people who care' (like my banker friend above). I guess that it's not that she didn't care, it's just that she no longer saw...