Links, links, links. Everyone talks about them, everyone knows they are important. Google just changed their algorithm to make it more strict on what counts as a link to Google. As with everything in SEO, when something is found to be important to rankings, black hat SEO professionals find ways to exploit it and then eventually the search engines catch on and either discount it or make it banworthy.
Be careful when choosing an SEO company. There are a lot of good guys out there and a lot of bad guys looking to take money from you. If it seems sketchy, it probably is. Make them show you evidence that their tactic is considered white hat or ethical. Especially with links. Often companies promising hundreds or thousands of links immediately are doing something that will hurt you in the long run. Only classic people like Link Moses Eric Ward are able to pull these things off and make them actually last that quickly. Many of these comanies pay for links or offer you links from pages they have set up specifically to link to your pages. Eventually they will be found out.
When it comes to small business, sometimes it only takes a few links to go from where many of you start, with 0, to being able to compete for some of the less searched but more efficient terms. For example, one of my clients, a hard working mortgage broker, just started a new site, so he is hurting for some factors such as length of time out there, etc. He of course started with no links, but just by doing a little campaign and gaining a few links he went from unable to compete for just about anything, to really being able to go after some terms that are relevant and will bring him good business. Small businesses can find those niche keywords that will allow them to compete with a handful of good links, rather than needing hundreds. This allows them to hire someone like me that specializes in small business SEO to get them that traffic without paying the big firms thousands per month, that they may not be even making themselves as a smaller company starting out.
There are a lot of things small or new sites can do for less than you think. Learn more at my site, The SEO Helpdesk.com or YouCanBeFound.com