Amount being spent you say, is that spent by the people buying t-shirt or the t-shirt company?
Yes. As I said, as long as the total size of a transaction is less than 10 kilobytes, and the value of every output is larger than 0.01 BTC, and the priority of the transaction is greater than the equivalent of 1 bitcoin day, the transaction can be attempted without fees at the moment. It doesn't matter who's doing the spending, only that the "spam filter" fee requirements aren't exceeded. Fee requirements are likely to change in the future as the exchange rate increases (it has changed in the past).
On the other hand, as bitcoin gains popularity, the available space in a block will become more valuable. As such, even if the "spam rules" don't require a fee, it may become nearly impossible to get a confirmation without a reasonable fee. It's possible that by then there will be third-party services that will provide methods for transferring bitcoin value off-blockchain.
Also you said;
"If you have inputs valued at 0.00000001 BTC (frequently received from SatoshiDice), they'd have to age for 10,000,000 days before they could be individually spent without a fee."
So for example;
I have a few of those 0.00000 transactions is there any hope for me to ever be able to spend bitcoins without having to pay a few? Or are was my first day in bitcoin world with a lot of small transactions messing it up for the rest of my life?
Well, as the exchange rate for bitcoins increases, the fee requirements are likely to be reduced. In the meantime, you could create a backup of your current wallet (to recover in the future after the outputs have aged and the fee requirements are reduced), and start a new wallet. You could also (as has already been mentioned by "DeathAndTaxes") send a single larger output to the wallet. Over time, as the "dust" ages, the wallet may occasionally include it with the larger output to "consolidate" it. Meanwhile the wallet will use the larger output for transactions and simply ignore the tiny ones.