I don't see how my point isn't valid. For there to be reasonable chance for purchasing power to hold between when you buy bitcoins and when your charity cashes them out to pay for things two things would need to hold: (1) the transaction would need to happen very quickly, and (2) the volume would need to be relatively small.
For the vast majority of people interested in making donations via bitcoin the whole process of buying them, sending them off to the charity, and the charity cashing them out isn't going be fluid enough to mitigate the very high chance that the money taken out in the end will be significantly less than what was put in. I don't think you need to look any further than the last 4 months to see that the odds are against retaining the original purchasing power. Some savvy people who are quick on the draw or lucky or both might be able to retain the original purchasing power or even increase the final purchasing power of their donation, but there are too many variables against that coming out true for the vast majority of cases.
I get that for a very small number of cases bitcoin is the only way transfer purchasing power. Sadly, as I've pointed out, compared to conventional means of donating there's a fairly high premium to make that donation. Make it if you want to. I'm just saying that odds are that a lot of purchasing power is going to get lost along the way.
My intention isn't to spread FUD. I'm just calling it as I see it.
I will grant you that for someone starting 'cold' it is not very practical to use Bitcoin as a means of making donations (though a reasonably savvy person, and especially one who was not opposed to using a Dwolla/Paxum-like solution or already had such an account could do it readily.) But you responded to someone who clearly already had an account at and exchange and could easily convert at will and could hold funds in USD or in BTC at his discretion.
I will also grant you that holding an account at an exchange is not the safest thing to do, and not for everyone. So far I have not been burnt here, but I am careful in initial research and in ongoing use.
But the argument that significant losses are even likely occur due to the falling price is non-valid. If the recipient is not cashing out quickly, that is their problem and not a difficult one to solve. With code if need be, and that would make more sense when smaller donations are trickling in.
It would be nice it one did not need to be somewhat nimble to avoid losing value in playing with Bitcoin, that that is the current shape of things. As I've said earlier, I expect that at some point a floor will set in based on what usefulness Bitcoin has and how nimble what remains of the user base becomes. The floor may have a tilt one way or another due to utilization and inflation. And like any market, will have some amount of volatility.