This is a common advertising practice among larger brands, and for good reason. It provides a filtering mechanism through which prospective customers identify themselves based on topics of shared interest.
For example, in 2012, Nike conducted a hashtag campaign using Pinterest, Twitter, and Instagram that asked fans to share how they planned to “#makeitcount” that year. The company advertised via print and digital media to focus attention around it. So successful was the campaign that Nike extended it into 2013.
Most social networks now incorporate hashtags, so it’s an easy way to get your message in front of prospects without the need for overt marketing tactics.