Having read a different topic, a person posted that he had spoken to a securities lawyer, and they had reached the conclusion that public trading on the "Global bitcoin stock exchange" (and hence any exchange in the US dealing with securities) would subject it to SEC and relevant laws. A security is defined as:
"(3) the term “security” means—
(A) a note, stock certificate, treasury stock certificate, bond, treasury bond, debenture, certificate of deposit, interest coupon, bill, check, draft, warrant, debit instrument as defined in section 916(c) of the Electronic Fund Transfer Act, money order, traveler’s check, letter of credit, warehouse receipt, negotiable bill of lading, evidence of indebtedness, certificate of interest in or participation in any profit-sharing agreement, collateral-trust certificate, pre-reorganization certificate of subscription, transferable share, investment contract, voting trust certificate, or certificate of interest in tangible or intangible property;"
US Code Title 18 § 513. Securities of the States and private entities.
Considering the fact that a securities lawyer has a far superior legal comprehension than myself, I concur that Bitcoins are not considered Barter. Also, it cannot be considered both a barter and a security, which I fallaciously argued earlier. However, as Bitcoin is a "debit instrument as defined in section 916(c) of the Electronic Fund Transfer Act" ("As used in this section, the term "debit instrument" means a card, code, or other device, other than a check, draft, or similar paper instrument, by the use of which a person may initiate an electronic fund transfer.") any Bitcoin exchange based in the U.S. is subject to the SEC and relevant laws. And, of course, in the globalized financial business sphere, all stock exchanges in the world are subject to similar legal provisions and all defintions of "securities" are likewise or very similar, and due to "harmonization" the laws and definitions are being aligned continuously.
So all Bitcoin exchanges, wherever situated are subject to the exchange laws of the host nation, as Bitcoin is a kind of "security", I contend. Exactly which tax laws that are applicable is beyond my current knowledge; although the only point that we have agreed upon so far is that gains on Bitcoin trades are subject to some kind of tax.
There is a reason that lawyers "practice" law. You can ask ten lawyers the same question and get fifteen different answers. Does it surprise you that a securities lawyer would see bitcoins as a type of security? A real estate lawyer would see them as real property, an Intellectual Property Lawyer would see them as IP etc etc etc.....
My background is in economics, econometrics, commodities, equities and derivatives so I am also biased. My opinion is based on what mostly resembles bitcoins in use and utility, I find this to be diamonds. If we had a willy wonka teleportation machine and could move diamonds instantaneously and securely across space they would function exactly as bitcoins do. Does Lil Jon have to wear a USB stick with 5000btc in it around his neck to give it another use and make you accept it as a physical good?
There is no way bitcoins are a security. Bitcoins are individual things. You could securitize bitcoins by creating a security that signifies ownership in a bitcoin (or bitcoins) and possibly trade that on a stock market but by definition a security is only a document ownership of some underlying thing.
As far as if bitcoins need to be taxed that depends on your jurisdiction. A blanket statement saying they are subject to some kind of tax is ridiculously broad.