LN is most useful for lager entities which hold users bitcoins, and move them on there behalf.
bitpay, bitfinex, changetip, etc..
will all be connected together via LN and allow users to move funds among these large site, in a cheap / instant / trustless manner.
I'm not sure I follow. If I want to pay Bob for a hamburger with BitPay, how would LN play into this? I have an open, pre-funded channel with BitPay, and BitPay has open, pre-funded channels with everyone I want to do business with? That's a *huge* sum of BTC to tie up.
If not clear, before using BitPay, I'd have to open a payment channel with BitPay, and fund it with as much BTC as I'm likely to spend with BitPay in, let's say, a month. That's a big chunk of change, but that's not all. BitPay has to keep a huge number of open channels with all of its users, and those channels all have to be funded. That's a huge chunk of change squared.