Jeff, in the context of very specific advertising targets, here are a few random thoughts that I hope may help.
1. Google AdWords retargeting. Give a very specific URL to person X to visit on your website. Make sure no one else knows about that URL. Then, set retargeting to show your desired ads later to anyone -- i.e., person X -- who views that specific URL on your website. Only the decision-maker, then, will see your ads so you don't waste money advertising to people who don't have a say. This same idea could be expanded to people who work for a given company. I don't remember off the top of my head, but I think you can set retargeting based on IP address. If you know your target company's IP address, then I think you can show your desired ads to anyone using that specific IP address. In case you don't know about retargeting, here is Google's general guide along with a Moz Whiteboard Friday.
2. Facebook custom audiences. You can upload a list of e-mail address, phone numbers, or Facebook user IDs as a set of specific targets in a Facebook ad campaign. Moz has more information here.
3. Twitter targeting. You can now target Twitter ads by e-mail address or user IDs.
Just three ideas to target a specific individual or group of people -- I hope that helps. Good luck!
