Youtube Video Response spam was pretty nasty. It did attract some attention for unique spam detection algorithms for video responses as well [0,1].
[0] Fabricio Benevenuto, Tiago Rodrigues, Virgilio Almeida, Jussara Almeida, Chao Zhang, and Keith Ross. 2008. Identifying video spammers in online social networks. In Proceedings of the 4th international workshop on Adversarial information retrieval on the web (AIRWeb '08), Carlos Castillo, Kumar Chellapilla, and Dennis Fetterly (Eds.). ACM, New York, NY, USA, 45-52. DOI=10.1145/1451983.1451996 http://doi.acm.org/10.1145/1451983.1451996
[0] Fabricio Benevenuto, Tiago Rodrigues, Virgilio Almeida, Jussara Almeida, Chao Zhang, and Keith Ross. 2008. Identifying video spammers in online social networks. In Proceedings of the 4th international workshop on Adversarial information retrieval on the web (AIRWeb '08), Carlos Castillo, Kumar Chellapilla, and Dennis Fetterly (Eds.). ACM, New York, NY, USA, 45-52. DOI=10.1145/1451983.1451996 http://doi.acm.org/10.1145/1451983.1451996
[1] http://www.iiitd.edu.in/~ashish/PST-2013.pdf