Are you great at something or good at "everything"?
It's generally easier to market a company or consultant with a specialty. There are already way too many "me too" companies (and developers), and a distinct brand and position makes it much easier to connect to potential clients - whether it's "hip websites for fashion conscious tweens", "affordable custom social networking apps" or "helping law firms to express their credibility online". Equally, it's much easier to market someone as a ColdFusion server monitoring and performance guru than as a generalized CF dev. The flip side is that the vast majority of the opportunities that arise are going to be within your general capabilities but not within your distinct specialty, so a brand driven approach requires a much more proactive approach to marketing your services as you're unlikely to just run into enough people who need what you do to build a profitable practice/business.
Do you position yourself as an expert or as a generalist? When you DO get specialty gigs, do you find on the whole that you have a better experience? Do they tend to me more profitable? More enjoyable?
Thoughts appreciated!
However I've always liked the idea of consulting firms that specialize in certain industries. When you become really familiar with an industry, it gives you an advantage over the competition because there's less getting up to speed and you know how to work with those types. And you're more likely to build resuable work (so long as you structure your contracts appropriately).