His team paid for "Sponsored Stories" to appear in some users' Facebook news feeds - regardless of whether they wanted to receive them.
President Obama's page received more than one million "likes" in a single day - compared with about 30,000 per day in earlier weeks. But some observers warned the approach could frustrate and dissuade voters.
It comes at a time when both President Obama and Republican candidate Mitt Romney are stepping up their efforts on social media.
The opponents each have a presence on a host of digital communities, including streaming music service Spotify, image-sharing network Pinterest and the Facebook-owned picture network Instagram - where Mr Romney has been busy posting pictures of himself at home with his family.
But users were quick to voice their annoyance as President Obama campaign advertisements and messages appeared within Facebook news feeds.
Source: BBC News
