My trips to Ireland have always left me feeling that its "terrible beauty" was a record of political misfortune; the arable land at the center gently dotted with Anglo palazzos while the Celts were driven to eke out a living on the hardscrabble edges of the sea. The economic prosperity the republic is now experiencing is wonderful if destabilizing of old cultural norms--and potentially of old tribal enmities.
You're certainly right that expressed outrage often bears little relationship to real cost-benefit calculations. Why the policy and press attention to Kosovo and not Rwanda? Here the possible culprits are racially selective sympathy and indifference on the part of the polity, selectivity on the part of the media and press (which may itself reflect the racial selectivity of the audience), and allegorical and historical parallels to the horrors of World Wars I and II. There's also a kind of slippage between humanitarian and self-interest arguments: The President's foreign policy address a few weeks before the bombing began stressed that if we didn't stop the killing in Yugoslavia now (humanitarian), our economic interests in a peaceful and stable Europe would be hurt later (self-interest).
Why apparel sweatshops? It can't just be that labor is resurgent on campus; else more would be happening on behalf of graduate student unions and farm workers. Maybe it's a kind of socially beneficial narcissism: Students can be galvanized most readily by issues that literally touch and concern them, like the insignia-emblazoned clothes they wear. Again, some selective sympathy and indifference: The plight of women and children in physically appalling labor conditions has visceral appeal.
Related to these issues is the problem of inference from anecdote. The Diallo shooting in New York has lowered the political popularity of the entire Giuliani quality-of-life program, even though even liberals have conceded over the last several years, sotto voce of course, that they're happier with less crime, the new Times Square, the cordoned homeless population, and liberation from squeegee men. How can one incident, however shocking or horrific, have such a broadly destabilizing effect on public opinion? The reverse is also true; public opinion can rally to a single sympathetic incident that then consumes a disproportionate share of public resources.
Assuming there is an economy of moral outrage, and that too much horror produces fatigue and withdrawal of attention from public affairs, perhaps selective attention is the best one can hope for.