Top 20 Largest Ad Networks in December 2012 (Buy Side)

What is the largest online Ad Network in 2012, for advertisers ? Here's a Top 20 list ranked by coverage, from comScore, published in Jan. 2013.

For Advertising Networks and Buy Side Networks, Google Ad Network ranked #1 with a 93.9-percent reach, followed by Specific Media (89.5 percent), Federated Media Publisher Network (87.3 percent), AOL Advertising (84.2 percent) and AT&T AdWorks (83.9 percent).

Top 20 Ad Networks/Buy Side Networks
Rank	Property			Unique Visitors (000)	% Reach
1	Google Ad Network**			208,074	93.9
2	Specific Media**			198,119	89.5
3	Federated Media Publisher Network**			193,453	87.3
4	AOL Advertising**			186,595	84.2
5	AT&T AdWorks**			185,757	83.9
6	Genome from Yahoo!**			184,556	83.3
7	Vibrant Media**			181,345	81.9
8	Real Media Group - 24/7 Access**			177,880	80.3
9	ValueClick Networks**			176,537	79.7
10	Casale Media - MediaNet**			173,681	78.4
11	Microsoft Media Network US**			169,861	76.7
12	Collective Display**			163,902	74.0
13	Tribal Fusion**			163,292	73.7
14	RadiumOne**			156,993	70.9
15	PulsePoint**			156,869	70.8
16	Burst Media**			155,355	70.1
17	Cox Digital Solutions - Network**			148,138	66.9
18	Rocket Fuel**			142,992	64.6
19	Adconion Media Group**			131,414	59.3
20	AudienceScience**			130,841	59.1
Total Internet : Total Audience		221,486	100.0