"Transaction spam" is the largest issue threatening the fledgeling currency called Bitcoin. A brief synopsis of the problem:
"SatoshiDICE" notifies gambling addicts of losing bets by sending them a transaction containing 1 satoshi back to their original address. A regular transaction fee is also included in this transaction. The problem is that this produces an unspendable and unprunable output. The output is unspendable because it is so small that it would cost more in fees than it would to send. It cannot be pruned because it has to stay around in fast storage to detect double spends, even though ironically it cannot be spent (developers, let me know if this description is technically accurate).
You see, you don't really know what you're talking about and that's leading you to draw the wrong conclusions.
If I have other coins, say 4 BTC, and want to spend 1.25 BTC, it's trivial to create a transaction with 4 BTC + 1 or more single-satoshi inputs, that pays 1.25 + 2.7500000x BTC change as outputs, and pay no fees.
So not only can they be spent, they can even be spent and pruned for free. Yes, I've done it myself.