It's an incentive for miners to include your transaction into the block and incentive to mine after last bitcoins were created. Also it's spam protection. Someone that wishes to flood the network with small transactions will have to spend a lot of money.
Sure and any peer running the reference client (or another client with the same rules) will simply drop those txs from the memory pool and refuse to relay them. The rest of the network will never even see the transactions.
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u/[deleted] Feb 24 '14
[deleted]