Yahoo is in serious talks with Tumblr to acquire the social blogging site, according to multiple sources familiar with the talks. The deal is not done, but could reach as high as $1 billion, Adweek has learned. Allthingsd.com was first to report on the talks between the two companies.

Such an acquisition could be just what CEO Mayer has been looking for to turn around Yahoo’s momentum; Tumblr has the potential to excite the engineering/Silicon Valley community (even though it’s based in New York) while recapturing the imagination of advertisers, who have grown to view Yahoo as big but stale.

While its revenue is modest, Tumblr has positioned itself as one of the few players in the digital ad world that is well suited for brand advertising.