In keeping with tradition, this summer is already bringing with it swimsuits and sunscreen, campfires and, yes, ad campaigns. Brands simply can't resist a good seasonal advertising effort, particularly if it's digital in nature. While summer is a tremendously important season for certain businesses (hotels and airlines come to mind), every brand stands to benefit from a relevant and well-executed campaign. Traffic to retail sites has been known to increase by at least 10 percent during the summer months as consumers prepare for vacations, outdoor activities, and back-to-school, and this uptick can be leveraged with promotional initiatives that play out online. Pinterest As a Source of Marketing Content From the…