This is serious, and may impact on you, or if you do SEO (Search Engine Optimisation) for a company your clients web sites.
the case of Interflora (those guys that sell flowers) www.interflora.com is quite a wake up call, and all those invloved in the SEO Industry should take heed.
read about the storyhttp://blogs.independent.co.uk/2013/03/01/interflora-suffers-seo-setback-as-mothers-day-approaches/
and the solutions / guide lines to preventionhttp://googlewebmastercentral.blogspot.co.uk/2013/02/a-reminder-about-selling-links.html
A video on the back link issue by Matt Cutts - http://en.wikipedia.org/wiki/Matt_Cutts
The moral of the story is that you reap what you sow, and if you sow weeds and problem plants, you will get weeds which you are unable to eradicate, as their seeds will continue to grow every season, and problem plants that mess your garden and spoil the experience of your visitors.
Think about where you advertise, and what your call to action message is, advertise in relevant places and be clear with your message. SEA's (Search Engine Algorithms) are getting bigger, and are looking at an awful lot more variables that they did a few years back.
User experience, and finding exactly what you have searched for are becoming more important to search engines and their controlling SEA's (Search Engine Algorithms), so your adverts need to be more explicit and closer to home. adverts that discuss off page / site topics and use words that are not on your landing page may cause your site some harm, so think clearly of where your adverts are placed and what exactly is the message and call to action statement in your advert.
Remember to use FUFISM and include your whole marketing teams experience as well as keeping the rest of your social media partners in the loop.
Always keep tabs on your stats and when they start taking a detour down south, find out why fast. the longer you take the worse the impact gets, and the harder it will be to recover.