[mike_hearn]

The OP was complaining that blockchain.info has outages (which it does), so there's one reason. But more generally, the whole point of Bitcoin is you don't have to rely on trusted third parties. You might as well say, "the bank can't really try to gamble with your money, it'd ruin its business". But it happens! Now block explorer sites can't gamble with your money, but they can do plenty of other things. The assumption that they won't do problematic things because it'd hurt their business is just as weak. E.g. what happens if they start charging you fees?

But more generally I wonder why people are doing this. If your app really needs indexed access to the entire block chain, you probably designed it wrong. If your app doesn't, then you could as well use local software.