It would be great to have Christian pop-ups all over the Internet, but who will pay the bills?
Pop-ups are irritating, however wonderful the message. You don't bring people to Christ by waving leaftlets in their face in the shopping mall, and you wouldn't by having pop-ups appear every five mins - you'll just annoy people.
The sleaze providers make tons of money and can afford the advertising. The average Christian site is run on a shoe string budget. That would be the case with my web page and will probably be the case with most Christian web sites. All we can do is the best we can with the resources God gives us.
And strangely enough, He provides just enough for what is absolutely needed. I get very worried about any church or Christian organisation that isn't struggling for enough cash.