Social media is a hot term right now that I believe a lot of people in the general public don't fully understand or don't use properly. Social media can be a powerful and effective tool for some and complete snake oil for others. I read and hear about people calling themselves social media consultants and experts who can leverage the viral nature of social media to increase website traffic, sales, and awareness for brands. In my opinion, this is only true if your marketing efforts are already viral in nature or the content your sharing is valuable to your following.
Clever advertising and marketing only goes so far. If you're lucky enough to get someone to your landing page, you still have to sell the person on your product. This is why you must focus on your product first - if you offer high-quality products or services and clearly define your value proposition and what separates you from your competitors, then your product will sell itself.
I do think people should build up a social following as they work on their product, but people must realize social media shouldn't be your only strategy for customer acquisition. Social media should supplement your brand awareness and outreach efforts, but should not be relied upon solely for marketing.
Joining every social network and frequently blasting your entire following isn't going to yield desirable results. A good example is Twitter - following as many people as possible and hoping they follow you back isn't going to do anything for you. Most likely they are following you for the same reason you're following them (to plug stuff).
Offer tips, helpful links, demonstrate your great customer service, etc. and you'll receive genuine followers that will actually digest what you're tweeting.
Lastly, it is of my personal opinion that hiring social media 'experts' or 'consultants' isn't the most effective solution to raising your company's social media effectiveness. Social media should be a conscious effort for all your employees. How you and your employees engage with the public and what you divulge and offer to the public will be much more effective than anything one person can do. Social media allows consumers a certain level of intimacy with their interactions with your company and using the right amount of cleverness, unwavering customer support, and having a great product can turn potential customers into paying customers that, in turn, become advocates for your company.