Well you determine what counts as spam and just don't propagate it. Fees are a part of the process of keeping spam out of the blockchain. Some people also count sending 'bitdust' as spam.. seemingly defined as anything less than 10k satoshis (or 1/10,000th of a bitcoin--obviously that definition would have to change over time if bitcoin continued to appreciate).
The real answer to your question though is 'off chain transactions' will likely become the way a lot of debts are settled. It's trivially easy to double spend coins that have been not confirmed into any blocks, so it's inevitable that this type of fraud will become more prevalent. As such, it makes things like 'buying coffee' with bitcoin really annoying, if I am going to have to wait 2-15 minutes for my transaction to get confirmed into a block it isn't really going to work. So B&M retailers will be forced to make their customers wait for transactions to confirm, or risk getting scammed (which breaks the whole "point" of bitcoin having lower fees than CCs).
Enter off-chain transactions. Retailers could either let you hold a balance there, or, more likely.. someone will pop up with a competitive off-chain transaction scheme; perhaps Ripple, perhaps something more like bitinstant; where balances are demoninated in bitcoin and retrievable in bitcoin, but day-to-day small transactions actually happen in a 'centralized' database and are only written to the blockchain upon cashing out. (note this is exactly what is happening with mtgox, where tons of coins exchange hands just within their system that don't get written to the blockchain until you cash out your coins).
The real answer to your question though is 'off chain transactions' will likely become the way a lot of debts are settled. It's trivially easy to double spend coins that have been not confirmed into any blocks, so it's inevitable that this type of fraud will become more prevalent. As such, it makes things like 'buying coffee' with bitcoin really annoying, if I am going to have to wait 2-15 minutes for my transaction to get confirmed into a block it isn't really going to work. So B&M retailers will be forced to make their customers wait for transactions to confirm, or risk getting scammed (which breaks the whole "point" of bitcoin having lower fees than CCs).
Enter off-chain transactions. Retailers could either let you hold a balance there, or, more likely.. someone will pop up with a competitive off-chain transaction scheme; perhaps Ripple, perhaps something more like bitinstant; where balances are demoninated in bitcoin and retrievable in bitcoin, but day-to-day small transactions actually happen in a 'centralized' database and are only written to the blockchain upon cashing out. (note this is exactly what is happening with mtgox, where tons of coins exchange hands just within their system that don't get written to the blockchain until you cash out your coins).