When looking at recruiting analytics, I've found there is a HUGE drop off in the number of applicants per job as compared to onsite interviews. Probably not telling anyone involved in recruiting anything they don't already know.
The whole "Quantity vs. Quality" thing.
Companies that look to and focus on social media to try and lower this disparity are spending their time on the wrong thing.
"There's a service that 92% of online adults use, with 61% of them using it daily for an average of 13 hours weekly. This service has click-through rates that are 6-times better than social networks, and on average it sees a 94% return on investment." ~ its called email.
Companies should focus efforts on talent pipeline building with a targeted email marketing strategy that follows permission based marketing rules and guidelines... rather than spending their time on social media broadcasting information. Time is finite and valuable, when you have to choose, choose wisely.