Very well put. If you find your self with a few spare million, I would think it is good stewardship to apply that advice to selecting charities, with as much care as you would investments. It also helps with the "purpose" aspect paul mentions.
It would be pretty frustrating if you quickly did a sizeable donation (sizable compared to the norm for that charity) and find out a month later about some scandal, or how only a small portion of what you thought was a donation really was a donation etc... you would just get on with life, but it would innoculate you against further causes in future which is a loss for everyone.
So good advice, think of it as an investment (in terms of dilligence, time etc).
That and giving stupendous tips and totally making someones day, that must be a whole lot of fun.