It currently isn't taxable, but laws will be laws and if law is changed to allow virtual currencies to be taxed (specifically for Bitcoin, and likely only for Bitcoin and its derivatives), then there will be the power to tax.  I guarantee there will be supporters for taxes, and enough lobbying to push it through.  What I'm saying, if governments are allowed full access to what you do on the web and on your computer, they will find a way to monitor what you spend and to whom.  It'd be a long list to explain how they could go about doing this, but I wouldn't say it's completely out the window.  We're safe for now, but if and when Bitcoin eats up a lot more than where we're sitting at right now, America, and any other country for the matter, will likely want in on it, and will find a way to swallow a percentage of your cash.


I have high hopes for Bitcoin personally   Today of course, it's not going to happen.  But I do believe Bitcoin is firmly grafted into society, and crypto-currencies aren't going to fall off the planet anytime soon.  Countries would either wait for the value of Bitcoin to stabilize, or simply transform the Bitcoin into a bill for dollars.  They wouldn't be able to draw Bitcoin from you directly by any means; instead, I believe they would require you to declare all of your addresses so they can monitor your wallet's activity.  After so long, they send you the Bitcoin tax bill and demand payment in USD (or whatever the country's currency is) or face prison time.  If they decide you're using undeclared wallets to transfer cash, they would probably attempt imprisonment for tax evasion, or claim you're laundering.

I'm certain there's several ways it could happen, however...  But as long as the Internet stays private, it's nothing to ever worry about.