I think the big problem here is that nobody has any clue what is cons utionally "obscene" and what isn't. The Supreme Court basically has punted on the idea of giving a definition and has left that determination to the norms of the local community. But the local community in 2008 is very different than the local community that existed 30 years ago or so. What's kosher in San Francisco might be seen as obscene in suburban Pennsylvania. Had this woman maintained her website in a different community, she might very well have never faced any sort of prosecution. But, given the current state of free speech law, that doesn't mean that the First Amendment was violated by her prosecution in Pennsylvania.
An even bigger problem with cyber obscenity is that what might be perfectly legal to display in, say, Thailand or Uruguay or Morocco might be deemed to be completely obscene in every American community. If it's legal where it's posted, I'm not sure it can be prosecuted where it's viewed. For instance, I don't know where 2 girls, 1 cup (given what I've heard, it sounds like a perfect example) originated, but it could be that it originated in some foreign place and isn't actually housed anywhere within the United States. If that's the case, no American prosecutor would likely be able to go after what would appear to be obscene material; if I decided to have a showing of that beauty in my house and charged admission to a bunch of my deviant friends, I might be getting closer to a prosecutable offense. If I'm displaying it myself, don't get the protection of the obscene material being legal somewhere else.