"such as Facebook and Twitter" 9,940,000
"such as Facebook and MySpace" 3,240,000
"such as Facebook and LinkedIn" 802,000
"such as Facebook and Bebo" 152,000
"such as Facebook and Orkut" 45,200
"such as Facebook and Ning" 16,900
"such as Twitter and Facebook" 3,460,000
"such as Twitter and MySpace" 328,000
"such as Twitter and LinkedIn" 261,000
"such as Twitter and Bebo" 14,600
"such as Twitter and Orkut" 6,790
"such as Twitter and Ning" 6,540
"such as MySpace and Facebook" 3,300,000
"such as MySpace and Twitter" 351,000
"such as MySpace and LinkedIn" 64,500
"such as MySpace and Bebo" 95,500
"such as MySpace and Orkut" 81,800
"such as MySpace and Ning" 2
"such as LinkedIn and Facebook" 232,000
"such as LinkedIn and Twitter" 136,000
"such as LinkedIn and MySpace" 28,300
"such as LinkedIn and Bebo" 6
"such as LinkedIn and Orkut" 6
"such as LinkedIn and Ning" 2,350
"such as Bebo and Facebook" 31,500
"such as Bebo and Twitter" 6,530
"such as Bebo and MySpace" 24,000
"such as Bebo and LinkedIn" 1
"such as Bebo and Orkut" 6
"such as Bebo and Ning" 0
"such as Orkut and Facebook" 21,000
"such as Orkut and Twitter" 4,140
"such as Orkut and MySpace" 3,900
"such as Orkut and LinkedIn" 986
"such as Orkut and Bebo" 3
"such as Orkut and Ning" 0
"such as Ning and Facebook" 6,020
"such as Ning and Twitter" 10
"such as Ning and MySpace" 2
"such as Ning and LinkedIn" 1,220
"such as Ning and Bebo" 1
"such as Ning and Orkut" 1

Results on Google as of June 3, 2011