Fast National ratings for Friday, March 12, 2010.
 
CBS' clear domination over Friday nights appears to be in jeopardy or, possibly, a thing of the past. 
 
For the second straight week since switching over to two hours of "Dateline" and premiering the genealogy series "Who Do You Think You Are?," NBC nearly won the night, putting a serious scare into CBS' normally sturdy procedurals.
 
Among adults 18-49, CBS won the night with a 1.8 rating, just beating NBC's 1.7 rating in the key demographic. FOX and ABC were close behind with a 1.4 rating, with The CW's 0.6 rating taking fifth.
 
Overall, CBS averaged an estimated 8.25 million viewers and a 5.1 rating/9 share. NBC had the same 5.1/9, but averaged 7.75 million viewers for second. ABC's 3.3/6 and the 2.2/4 for FOX followed. The CW's 1.1/2 was good for fifth.
 
CBS' "Ghost Whisperer" started the night in first with a 4.9/9 and a 1.9 demo rating. The second week of NBC's "Who Do You Think You Are?" did a 4.5/8 and pulled in more viewers and a slightly higher demo rating than in its premiere. ABC's "Supernanny" had a 3.2/6 for third, leaving FOX's repeat of "House" in fourth. The CW's repeat of the "America's Next Top Model" premiere was fifth with a 1.2/2.
 
In the 9 p.m. hour, NBC's "Dateline" did a 5.2/9. CBS' "Medium" had a 5.1/0, but averaged more viewers than NBC and won the 18-49 demo with a 1.8 rating. ABC's "Supernanny" had a 2.8/5 for third, edging the 2.5/4 for FOX's "Kitchen Nightmares." The CW trailed with the end of "ANTM" and an encore of the "High Society" premiere.
 
In the 10 p.m. hour, again it was "Dateline" taking the top ratings with a 5.5/10. CBS' "Numb3rs" finale -- certainly the season's last episode, but possibly the series finale as well -- did a 5.4/10 for second, but averaged more viewers than "Dateline" and tied for the hourly win in the key demo. ABC's "20/20" was third.
 
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.