Lobbyists ultimately want to convince elected or appointed officials to support or oppose something. A viral campaign is a cheap way to pass information on to a targeted audience with immediate results. It could be directed at specific officials, or it could be directed at a segment of voters who could then speak out in favor of or opposed to a particular cause.
Advocacy groups are increasing their use of viral videos. The landscape is changing so fast it is impossible to describe it. So, here are a few examples of what advocacy groups are doing, click
A great example of a lobbying campaign going viral was a video posted by former Congressman Bob Livingston (R-LA) opposing American recognition of the Armenian Genocide