Here is a little sampling of local numbers to consider from Search Engine Land (along with some handy attributions):
* As much as $500 billion in off-line purchases was influenced by the internet in 2007 (eMarketer)
* 89% of consumers making in-store purchases in key categories have conducted research online (BIGResearch)
* 82% of people using local search sites followed up with an offline action, e.g. in-store visit, phone call (TMP Directional Marketing)
So even though the local advertising market is $100 billion, and the web has only a small portion of that, it is already influencing to the tune of $500 billion. That's a whole lotta clams. And it's only going to grow.
The skinny is pretty simple. In order to compete in any market, a web presence is important. The local market is most certainly one of them. And any business who doesn't jump into the next step in technology will be left behind.