Reading through the Lightning Network Paper, it seems that amounts sent through an intermediate node use the Hash Timelocked Output construction. The thing I'm concerned about with HTLCs is that they actually require their own output. Simultaneously, the transactions they are in must also be broadcast-able if the other party goes offline or become uncooperative.
So, let's look at a scenario where Alice wants to send 1 satoshi to Carol, through Bob, with whom Alice and Carol both already have payment channels open. Alice sends bob a new commitment transaction with 1 satoshi deducted from her balance and a new HTLC output for 1 satoshi. Bob sends the same type of channel update transactions to Carol. The problem is, though, that HLTC output would be considered dust if it ever did actually need to be broadcasted! So this cannot be considered a valid guarantee of payment, since the transaction would not even propagate on the network.
Is that a problem? Part of the excitement over the LN is that you can send really small amounts, but it seems to me that you can't actually send smaller amounts than you could in a real bitcoin transaction, because you have to be able to broadcast the transactions if the other party doesn't cooperate or goes offline.