Social network Tumblr is in need of a new president.

John Maloney, who served as president for the past four years, resigned this past weekend, according to the Wall Street Journal.

"People familiar with the situation" told the Journal that Maloney's skills as a general manager became less relevant as the company increased in size to 100 employees and brought other department executives into the fold.

Maloney himself seemed to concede his lack of prowess in running a large company, even telling the board earlier this year that he was thinking of leaving.

"I am a good operator," Maloney told the Journal. "Am I one of those big network operators? That is not particularly interesting to me nor does it play to my strengths."

In the wake of Maloney's departure, Tumblr is also venturing into a new territory once thought off-limits -- advertising.

Tumblr CEO David Karp has in the past shown no interest in putting ads on the site, seeing it as a last resort to make money.

But starting this week, the company will test the waters with a few advertisers displaying ads on the site's dashboard and directory pages, according to the Journal. The goal is to show ads that tap into the "visual nature" of Tumblr.

If done the right way, the ads would help Tumblr achieve a strong source of revenue. The company recently announced that it's now hosting 50 billion blogs and more than 20 billion posts. Grabbing 4.5 billion impressions per week, the site would certainly prove attractive to advertisers.

"Tumblr will have a shot at building a meaningful ad platform," Bijan Sabet, a Tumblr director, told the Journal. "There is too much evidence of something important happening here for advertisers not to care."