Deciding TO be a 'Jack-of-all-Trades'

Fairly early in my career, I was an expert with a particular database and programming language. Unfortunately, that particular database lost the 'database wars', and I discovered that my career options were ... limited. After that I consciously decided that I would never let myself become boxed in like that again. So I studied everything I could get my hands on: Windows, Unix, C, C++, Java, C#, Perl, Python, Access, SQL Server, Oracle, Informix, MySQL, etc. Whatever tools and technologies are new or unusual, I became the 'go-to-guy' -- "Ask Craig, if he doesn't know it, he'll learn it." As a result I've worked on all sorts of projects, from embedded systems for environmental telemetry to command and control systems for missile defense.

The only problem I've ever had is with companies that insist on pidgeon-holing me into a specialty, when my specialty is being a generalist. [EDIT: Also known as a Polymath or Renaissance Man or multi-specialist.]

Something to keep in mind ... what's the half-life of knowledge in high tech? It tracks with Moore's Law: half of everything you know will be obsolete in 18-24 months. An expert who chooses the wrong discipline can easily be undermined by the press of technology; a generalist only has to add some more skills and remember the lessons of the past in applying those skills.