I think you have to try a combination of approaches to first front load the site with content depending on the type of content you need (listings, reviews, articles or posts, comments). People don't want to see an empty site, and it will be difficult to bring them back if they get a bad first impression (empty site, non-existent community).

Some tactics you can explore:

1. Tap into your network and request participation;

2. Recruit "beta users" who get special perks for being early adopters and contributors;

2. Try crowdsourcing sites for lighter content contributions and community participation*;

3. Hire "sales" people to solicit content for you (this could be anything from offering free initial listings if you are building a directory or identifying appropriate content and asking permission to syndicate on your site);

4. Hire writers to contribute core content;

5. Advertise strategically to drive traffic for potentially more contributors and participators.

People want to write and contribute where they see others writing and contributing.

*While I don't endorse it, some people use sites like Fivver where for a nominal fee, you can get people to do small tasks including contributing content or commenting.

Honestly assess your strengths and focus on those. Partner, outsource, leverage resources and hire in all other areas to bring your product or service to bear.

A mistake many entrepreneurs make is to try to do it all. We may brag we "wear many hats," but what we really do is "roll up our sleeves" as needed then too often get bogged down in areas where we have little or no experience. We tend to get in our own ways by trying to do it all.

We get farther and faster when we leverage the resources and people who can do what we are trying to do more efficiently and effectively than we ever could because it is what they are good at doing.

(Context: I've started and run over half a dozen companies and have seen the most success where I've hired in areas where I am weak and played to my strengths. I've also failed miserably when I tried to do it all or partnered with the wrong people who held on too tightly and inhibited growth).

Three main things:

1. First mover advantage - There were others around the same time - Jaiku, Pownce, Plurk, Identi.ca, etc. - but they didn't get critical mass quickly enough.

2. "Disruptive" product - Who knew a new online platform could totally transform the way we communicate and consume content.

3. Open API to encourage ancillary app development. The rush for 3rd-party app integrations created a zeitgeist of innovation (and future acquisitions for the company).

I'd also say that the simplicity and focus on limited features was an advantage. And nimble response to its early adopter usage patterns and requests (ex: integrating "retweets" and hashtags into the product feature set).

(For context, I started an early Internet company in 1995, a social media marketing firm in 2005 before we called it social media and began using Twitter March 2007.)