There are differing opinions on whether Facebook and Twitter are competitors, but in the competition for monthly unique visitors, Facebook provided a great assist to Twitter in August, and the social network helped out MTV.com, as well.

According to the latest examination of the top 250 websites by Kantar Media Compete, Twitter received 26.6 percent of its traffic in August from Facebook, representing more than the combined total for Google and Yahoo.

The reverse did not hold true; although Facebook accounted for 22.7 percent of outbound referrals from Twitter, only 0.37 percent of Facebook’s incoming traffic was referred from Twitter.

Just 1.22 percent of outgoing referrals from Facebook were to Twitter, reflecting the lopsided nature of referrals between the two social networking giants. that’s mainly due to thefact that Facebook draws more traffic than Twitter, and many Twitter users access the service through third-party tools like HootSuite instead of going to the microblogging site directly.

Both sites set all-time unique-visitor highs in August, with Facebook tallying 155.8 million, up nearly four percent compared with July and 22.1 percent versus August 2010.

Twitter got 36.5 million, up 12.7 percent compared to July and 27.6 percent compared to August 2010.

The return of “Jersey Shore and the buzz ahead of the “Video Music Awards helped drive MTV.com to a 45.8 percent jump from July and a 24.9 percent jump versus August 2010, with Facebook playing a role, as well.

Traffic referrals from Facebook accounted for nearly 14 percent of MTV.com’s traffic in August, but unlike the comparison with Twitter, Facebook benefited from MTV.com, as well, with nearly 19 percent of MTV.com visitors going to Facebook.com immediately thereafter.