Pornography is not just more accessible with the Internet, it is more dangerous. There are now vast networks of child exploitation rings operating throughout the world. They buy, sell and trade not just child porn but children. While porn involving consenting adults might be harmless, child porn certainly is not.
Agree with #4. Before 1990, the FBI had child pornography rings pretty much run into the ground, and we had much fewer cases of such crimes to prosecute. The internet changed everything, child pornography cases have exploded in number, size and scope, and it seems almost impossible, or at least much more difficult to legally combat.
I think "mainstream" pornography (for lack of a better term) has become more widely socially acceptable because of the internet, and because there is no social stigma attached to viewing it in private. What used to have to be bought in public at stores can now be accessed in the home, so more people have done so than would have in the past, before there was internet.
I think the biggest change has been the way that the Internet has made pornography completely widespread - anyone with an internet connection can access pornography with ease, whereas before it was far more restricted. This has had massive implications for socially unacceptable forms of pornography such as pornography that shows the abuse of minors. The problems of restricting such sites make it a bigger challenge to control the flow of such material.
I think that the internet has changed the theoretical nature of what defines "local standards." In the U.S. Supreme Court, Miller v. California, the court rendered a decision that argued pornography and explicit material is able to be defined by localized standards and communities. The worldwide nature of the internet has changed that to a great extent. The ability to limit children's access to pornography has also become more difficult. Prior to the internet, distributors of pornography were able to be stringently identified and sanctioned if they distributed to minors, or those under legal age. The worldwide nature and ease of access in the internet has altered this aspect, as well. Sites now have voluntary measures where users have to accept that they are of age, making it much more difficult to sanction those who cater their services to minors. I think that these are two of many issues where the internet has transformed the debate regarding pornography.
The internet has changed the debate on pornography in a number of ways, depending on what aspect of the debate you are talking about. Since you have posted this under law, let me talk a bit about the legal implications of the internet for pornography laws.
The controlling case on obscenity set forth the "Miller Test" for whether something is obscene. One of the prongs of that test was about community standards. A jury had to determine whether something was obscene using the standards of their community. With the internet, the notion of community is much broader. Whose community's standards do we apply now? Those of the people where the pornography was produced? Those of the typical user of the internet? Those of the community where the pornography was viewed?
Depending on how you answer this, pornography on the internet might always be obscene (when judged by very conservative community standards) or never obscene. This has complicated the debate over pornography.