The FBI, law enforcement groups, and the Intelligence Community like it; BTC leaves trails and localizes evidence of guilt in some significant ways that make their job easier. They probably don't like BTC mixing services all that much, but that just means that they are at a slightly higher priority for monitoring and takedown.
The IRS on the other hand won't like a deniable currency which can't be cleanly audited if they can't correlate transaction id's to wallet holders cleanly and universally. Note that for any individual case it doesn't bother them, but the existence of a statistically significant population using a means of exchange that doesn't automatically report everything to the .gov (like your us based bank account does, read the fine print on your account docs ) is a vector for normalized tax fraud and off the books transactions, which they don't like, but not as much as they don't like cash in denominations larger than $20 bills.
Other major players in the US .gov who might have an opinion; the State Dept. worries about it's use for terrorism and hawala style money exchange, and the Treasury and Federal Reserve may regard it as a potential wildcard in their efforts to manage the economy.
Do expect some regulation of BTC, for instance efforts to require reporting of currency in and currency out; efforts to require linking BTC addresses to PII ( o hai coinbase.com ); and so forth.
Certain services are riskier than others. For instance I wouldn't recommend running a BTC mixer/anonymizer unless you are the wealthy and well-connected nephew of the president of a country with a UN seat; or live and operate somewhere past the horizon of US jurisdiction. At a minimum you would be labeled as providing material support for terrorism, at the utmost, you would be a prime target for subversion ( pro-tip, if your favorite mixer has an unexplained three-day outage and the CEO is not seen on video explaining in detail which storm took out which datacenter... your anonymity is no longer assured and you shouldn't use it for naughty things... )
Unfortunately, anonymous remixing is one of the few ways that BTC-only bank can hope to earn a return, so that will be one of the major tensions of the BTC economy for a few years.
Sorry, I sometimes make assumptions that many if not most of the people here have had at least some exposure to the language used in data security policies.
As far as I see it, it is not really a currency but rather a tool. A tool that remains operational so long as it has any "value" at all.
Sure, but having it declared illegal would definitely restrict the growth potential of the currency. At the moment its proponents envision/fantasize about it becoming huge and general-purpose, with a presence in the physical world (see bitpay etc). If a large nation like the US were to declare it illegal would certainly put a dent in that.
I disagree with a lot about BTC, in terms of the economic choices made in its model rather than the technical ones, but I find it continually fascinating to watch it as a phenomenon.
Or one is subjugated by man with more guns, but still he finds a way.
I doubt it will become huge and general purpose, but it will serve well for some services.
And do not forget, the nation does nothing, there is few people that declare and change.
I see "bitcoin" as a currency not too unlike I see "paypal" as a currency. That is, not particularly.
Why foolish? Risky, but not necessarily foolish. The bitcoin exchange rate has been going up all the time. Even with simple strategies such as dollar-cost averaging you would probably have done pretty well within the last couple of years.
It's not unheard of for a government to do something like this, my understanding is that it was done with gold at some point.
The will use an excuse such as terrorism, money laundering (because it competes with HSBC and similarly too big to fail banks), drugs, or whatnot.
How can they enforce it ? block the protocol ? ban tor too ? I think it is more likely they'll use any mean available to stop bitcoin from becoming mainstream. In particular, all the payment processors are a bit iffy with bitcoin, instead of embracing them.
Seems like Paypal, Visa, Mastercard, AMEX, diners and the various banks are to bitcoin what mpaa, riaa, GEMA and what not are to copyright, some sort of MAFIAA imposing their dead business model.
Do you know how many governments have acknowledged bitcoins ? Is it legally a currency or just some collector's trading of post stamps and things like that?
If they succeed, which still will be hard, I'm not entirely sure Bitcoin will continue to be that usable in spite of other decentralized ways of exchange like http://bitcoin-otc.com/ or http://localbitcoins.com
The US government hasn't killed online gambling, but they've certainly put a huge dent in it.
I expect the US government will step in in the not to far future and severely restrict the ability to legitimately exchange Bitcoins for dollars. I'm not passing any judgement on Bitcoins themselves, it just seems unlikely to me that people in places of power will be ok with an independent currency.