Upon watching, I realize why I had never heard of it before. It was because the movie isn't very good. It suffers from some pacing issues that probably evolved from the director trying to build suspense by having lights flicker but our main cast stay together for most of the movie. The movie would have been better served with a larger cast (group of survivors) being picked off in various ways to establish "the rules." What we get is a lot of confusion and the exposition of what the rules are after the fact.
Hayden Christensen didn't suck, so that was surprising, but Thandie Newton's performance wasn't that good. Leguizamo and the kids did all right.
My biggest issue with the movie is that nothing is explained. We don't find out how Leguizamo lived in the dark for 3 days only to be killed by it upon finding others. We don't find out anything about the nature of the darkness or how it causes electricity, even combustion, to not work. Sure it is likely supernatural, but the days get real short and the nights last forever. That is some pretty strong magic. We also don't find out how widespread it is. Why is the movie called vanishing on 7th street when an entire city full of people disappeared.
The DVD has an alternate ending special feature. I hope you don't waste your time watching it. Whoever put it together doesn't uderstand what an alternated ending is. An alternate ending is an ending that has been changed in some fundemental way so that the movie ends differently. It is not how many different ways you can edit the last two minutes of footage or at what point you start the music to take you into the credits.
Overall-The movie was a disappointment. It could have been could and had a great concept but was executed at an incredibly poor level. The studios realized this and that is why you have never heard of this movie either. It has cussing, but no graphic violence (I mean people disappear, but that is it) or adult content. I would say 10 and up should be safe as long as you don't object to them seeing bad movies.