Facebook pages are far more detailed than Twitter accounts. They allow a product to provide videos, photos, longer descriptions, and testimonials where followers can comment on the product pages for others to see. Facebook can link back to the product's Twitter page, as well as send out event reminders. As of May 2015, 93% of businesses marketers use Facebook to promote their brand. A study from 2011 attributed 84% of "engagement" or clicks and likes that link back to Facebook advertising. By 2014, Facebook had restricted the content published from business and brand pages. Adjustments in Facebook algorithms have reduced the audience for non-paying business pages (that have at least 500,000 "Likes") from 16% in 2012 down to 2% in February 2014. 
In 2012 during Hurricane Sandy, Gap sent out a tweet to its followers telling them to stay safe but encouraged them to shop online and offered free shipping. The tweet was deemed insensitive, and Gap eventually took it down and apologized. Numerous additional online marketing mishap examples exist. Examples include a YouTube video of a Domino's Pizza employee violating health code standards, which went viral on the Internet and later resulted in felony charges against two employees. A Twitter hashtag posted by McDonald's in 2012 attracting attention due to numerous complaints and negative events customers experienced at the chain store; and a 2011 tweet posted by a Chrysler Group employee that no one in Detroit knows how to drive. When the Link REIT opened a Facebook page to recommend old-style restaurants, the page was flooded by furious comments criticizing the REIT for having forced a lot of restaurants and stores to shut down; it had to terminate its campaign early amid further deterioration of its corporate image.
The fee structure is both a filter against superfluous submissions and a revenue generator. Typically, the fee covers an annual subscription for one webpage, which will automatically be catalogued on a regular basis. However, some companies are experimenting with non-subscription based fee structures where purchased listings are displayed permanently. A per-click fee may also apply. Each search engine is different. Some sites allow only paid inclusion, although these have had little success. More frequently, many search engines, like Yahoo!, mix paid inclusion (per-page and per-click fee) with results from web crawling. Others, like Google (and as of 2006, Ask.com), do not let webmasters pay to be in their search engine listing (advertisements are shown separately and labeled as such).
Digital marketing is defined by the use of numerous digital tactics and channels to connect with customers where they spend much of their time: online. From the website itself to a business's online branding assets -- digital advertising, email marketing, online brochures, and beyond -- there's a spectrum of tactics that fall under the umbrella of "digital marketing."