RebelMouse funding shows growing interest in personal social hubs

One of the trends I’ve watched with interest over the past few years is the growth of personal social aggregation hubs.
As people got tired of investing their entire web presence in fairly restrictive social networks that don’t play nice with one another and wanted some of their own namespace on the web (but didn’t necessarily want to create their own website), new sites like About.me, Flavors, and social hub aggregation hubs like RebelMouse popped up to fill a void and give a central place for people to aggregate their identities and streams.
The trend began in 2008 and 2009 with the founding of Flavors.me, and it started to gain momentum in 2010 with the launch and subsequent acquisition of About.me by AOL (only later to be spun out again).
And while Flavors.me is now owned by business card maker Moo, About.me’s founders saw enough potential in the business to buy AOL out of its investment and re-spin it out as an independent earlier this year. RebelMouse, which has seen solid growth with a total of 300,000 sites built, has garnered enough attention to get a significant funding round of $10 million from a variety of investors.
Will the growth continue? It likely will, but it also has to fight abandonment, as I would venture to say a significant number of RebelMouse’s 300,000 are  “ghost-sites” that are neither updated or visited regularly. The same is probably also true for About.me. However, the bigger challenge for both will be pushing their users into premium tiers, which appears to be one of the key strategies for both sites.
While the freemium model is a common strategy for many consumer services like blogging platforms and some social networks (like LinkedIn), it can be a tough road in a world where sites like Tumblr give most everything away for free (including personal domains, which both RebelMouse and About.me charge for). Because of this, I think premium conversion is going to be a tough sell unless these companies add significantly more value than simple social identity and stream aggregation.
They could pursue other forms of monetization, which I speculated about back in February, and one of the most obvious would be to integrate commerce features. With the rise of embeddable commerce tools for any site, there’s no reason why these sites couldn’t easily allow for sales of digital goods.