It really bugs me that I have to somehow pick which thing to care about, as if I can't be sad for both - and as if Amy Winehouse was somehow less of a person because she was famous/an addict.
I have noticed this about the way certain things are analysed here in the UK. It may be that I'm just noticing it more here. But they (journalist, talking heads...) seem to hunt around for the sticky point - the rub - and juice it. The guardian has a column where the writer dissects environmental actions and tries to show where even the most altruistic act actually has negative consequences - like when you wash out a tin to go in the recycle bin you actually waste water. I understand the point but a lot of times they leave you high and dry with no good answer. I suppose it is meant to prod us into thinking more about things.
Comparing our responses to different tragedies is the same sort of armchair phychology - like the 'writer' guy in the bar who doesn't engage with the people around him but constantly examines them.
Compared to the tsunami in Japan, these things are small potatoes....but Haiti is worse...and Somalia worse still....
But why do that? I agree that we don't have a limited pot of feelings, and perhaps we have different levels of concern running concurrently.