Earlier this month, Brafton reported that LinkedIn hit 100 million members. The professionally-oriented network is making gains (which is great for B2B social media marketing), but data suggests it still has a way to go before it catches up to the likes of Facebook and Twitter.

A report from The Media Audit, provided to eMarketer, reveals that U.S. consumers are logging into LinkedIn at higher rates than Twitter. While Facebook logins still lead by a wide margin (with 48.2 percent of the population signing into Mark Zuckerberg's social site in 2010), the B2B-friendly network boasted monthly visits from 11.5 percent of the population, whereas Twitter saw sign-ins from 9.6 percent.

Similarly, Brafton has reported that comScore's Digital Year in Review showed that LinkedIn saw more unique visitors than Twitter in December of 2010. LinkedIn boasted 26.6 million unique visitors, while Twitter saw 23.3 million.

Nonetheless, Twitter (and Facebook) have an edge on LinkedIn in terms of users' frequency of visits. A survey from Wedbush Securities relayed by eMarketer indicates that more than two-thirds of Facebook users (66.2 percent) visit the site multiple times per month – with 42.4 percent visiting multiple times per day. More than 16 percent of Twitter users sign in several times per month. LinkedIn, on the other hand, gets multiple monthly visits from 11.8 percent of its users.

This indicates that social media marketers should maintain an active presence across social networks in order to increase their chances of engaging audiences with timely Tweets, posts and LinkedIn shares. Of course, LinkedIn's monthly (and daily) visits may soon start to rise in light of the network's recent launch of LinkedIn Today – a customized news aggregator that attracts users with the latest trending headlines related to their industries.