I have copied at the bottom of this message what appears to be the version of the law as passed. The law has several elements but the key is "misleading" domain name and "intent to deceive."
I believe that any name that does not clearly indicate the sexual nature of a site (the law say having "porn" or "sex" in the name is ok) runs a risk of violating the law. Therefore, any name without "sex" or "porn" in it better first go to an intermediary page. Let's say you have "breast.com." I would probably have a page that has two links: Link 1: Search for "breast" on the Internet; Link 2: For Adult Material, visit "porn.breast.com." It should have a warning for those under 18 to go elsewhere and instructions on how parents can filter, etc. I believe with such an intermediary page, it cannot be possibly held that you are intending to "mislead" anyone. Furthermore, making the domain that ultimately points to the porn site a third-level that includes "sex" arguable falls within the safe-harbor provision of the law.
DISCLAIMER: THESE ARE JUST MY THOUGHTS and NOT legal advice. It is not clear how this will be enforced. I believe a problem with the law is that it is vague and, potentially, violative of the First Amendment. However, certainly those engaged in the online porn business should proceed conservatively with caution. The only real safe way is to wait and see how the law will be enforced.
`Sec. 2252B. Misleading domain names on the Internet
`(a) Whoever knowingly uses a misleading domain name on the Internet with the intent to deceive a person into viewing material constituting obscenity shall be fined under this title or imprisoned not more than 2 years, or both.
`(b) Whoever knowingly uses a misleading domain name on the Internet with the intent to deceive a minor into viewing material that is harmful to minors on the Internet shall be fined under this title or imprisoned not more than 4 years, or both.
`(c) For the purposes of this section, a domain name that includes a word or words to indicate the sexual content of the site, such as `sex' or `porn', is not misleading.
`(d) For the purposes of this section, the term `material that is harmful to minors' means any communication, consisting of nudity, sex, or excretion, that, taken as a whole and with reference to its context--
`(1) predominantly appeals to a prurient interest of minors;
`(2) is patently offensive to prevailing standards in the adult community as a whole with respect to what is suitable material for minors; and
`(3) lacks serious literary, artistic, political, or scientific value for minors.
`(e) For the purposes of subsection (d), the term `sex' means acts of masturbation, sexual intercourse, or physcial contact with a person's genitals, or the condition of human male or female genitals when in a state of sexual stimulation or arousal.'.
(b) CLERICAL AMENDMENT- The table of sections at the beginning of chapter 110 of title 18, United States Code, is amended by inserting after the item relating to section 2252A the following new item:
`2252B. Misleading domain names on the Internet.'.