Facebook is starting to see traffic drop in the U.S. and Canada, but the social giant's reach continues to expand.

Inside Facebook reports that traffic to the social giant is slowing, and Facebook is seeing fewer new visitors than in previous months. Nonetheless, the company is moving toward 700 million monthly users, and it is still a social marketing must.

Facebook gained 11.8 million users in May, compared to 13.9 million in April. The source notes that this is much slower growth than the company has generally seen in the past year, with Facebook seeing 20 million new members in a typical month.

Moreover, the site lost American users for the first time in a year, dropping from 155.2 million U.S. users at the start of May to 149.4 million leading into June. (It also reported losses in Canada, down 1.52 million users over the course of last month.)

In spite of these dips, Inside Facebook suggests more monitoring will be needed before analysts can claim any downward trends for the site.

Indeed, as these reports suggest Facebook is losing ground, data from last week's SMX Advanced conference suggests it is gaining marketing power: Facebook shares are common to 61 percent of the top results across more than 10,000 keyword queries, suggesting the social site is an important way for SEO marketers to gauge their online credibility. With this in mind, marketers will still want to share high-quality content with their fans.

Plus, socially advocated ads on Facebook are increasingly proving their worth. Brafton has reported that Sponsored Stories boast 46 percent higher CTRs than ads without social context, and Inside Facebook recently said that targeting Facebook fans reduces acquisition costs of purchases by 15 percent.

Katherine Griwert is Brafton's Marketing Director. She's practiced content marketing, SEO and social marketing for over five years, and her enthusiasm for new media has even deeper roots. Katherine holds a degree in American Studies from Boston College, and her writing is featured in a number of web publications.