I hate expressions which are not defined, because that makes reports like this impossible to decipher:

PHILADELPHIA – About 1 percent of Web sites indexed by Google and Microsoft are sexually explicit, according to a U.S. government-commissioned study.

Fine, but precisely what does the phrase “sexually explicit” mean? Literally pornographic pictures? I don’t think so, because otherwise, they’d have used the term “pornographic” or “legally obscene” material.
And in the very same article, Salon.com and others express fears that it might include things that most reasonable people do not consider pornographic:

The plaintiffs, including Salon.com, say they would fear prosecution under the law for publishing material as varied as erotic literature to photos of naked inmates at Iraq’s Abu Ghraib prison.

I’m sorry, but “sexually explicit” sounds like weasel wording introduced into this debate by people who’d like to censor a lot more than pornography.
I would note that the term “sexually explicit” was used countless times by mainstream media and by innumerable bloggers to describe the emails and text messages between Congressman Mark Foley and the pages, yet the language involved discussed things like “feeling horny” and the type of underwear being worn. Yet no pornographic pictures were exchanged, and it isn’t even clear that frank sexual solicitations ever occurred.
If that is “sexually explicit,” then what isn’t?
Would blogs discussing the Foley matter (or, say, Monica Lewinsky’s semen-stained blue dress, or Bill Clinton’s opinions about oral sex) be sexually explicit?
I’d also note that plenty of songs are said to contain “sexually explicit lyrics.” (“96 Tears” had to be changed from its original “69 Tears.” The Rolling Stones’ “Let’s Spend the Night Together” was banned from television.)
Now that I think about it, has this post now become “sexually explicit”?
What business is it of the government if it is? Why do my tax dollars fund studies like this?
As to definitions, a site called NetSafeKids makes a stab at it:

On this Web site, NetSafeKids uses the term “sexually explicit material” to mean material–text-based, visual, or audio–that depicts sexual behavior or acts, or that exposes the reproductive organs of the human body. From common usage, “pornography” can be seen as usually involving sexually explicit materials.

What is text-based material that depicts sexual behavior or acts? That would seem to include any accurate discussion of sexual intercourse (i.e., a penis penetrating another human orifice) or sexually fetishistic behavior, even though that might have absolutely nothing to do with titillating the reader, and might not cause the average person to become aroused. And how on earth could the intent of the writer ever be determined? (For example, if I declared truthfully I am not at all turned on by the idea of being tied up and whipped with painful nipple clamps on me, some reader I can’t control might be turned on by that.)
It is one thing to combat genuine pornography, but I don’t like this movement against “sexually explicit” material. I think they’re going to need to find a more accurate term.
As it is, I think I do a pretty good job of keeping this blog free from obscene material and language. I try not to even use four letter words. Yet my blog has been censored anyway by the net nannies.
I’ve long suspected that the goal of some of these people is broader than pornography.