I've been a Lisp hacker for years -- Symbolics Lisp Machine in my bedroom, coded in at least a half dozen different Lisp dialects -- but I ended up using Smalltalk for my startup. Treating Lisp's "rehabilitation" as a mere branding exercise shows just how screwed the Lisp community still is, and is symptomatic of the underlying issue. (By "Lisp", I mostly refer to Common Lisp.)
Lisp's problem is a meta-problem. The community is actively resistant to advancement, change, and evolution in the language. Attempts to modify (or even clarify) aspects of the Common Lisp standard are tedious exercises in futility, but the standardisation straitjacket is still seen as a good thing. A bit strangely, this resistance to change existing standards is accompanied by a slowness to standardise (even informally) anything that isn't already. The end result is that there's still no reliably portable way to write networking code in CL.
And this is why Lisp is unpopular.
The stasis is sad and ironic, given Lisp's hackerdom beginnings. Rather than wonder why, in 2009, so few are using Lisp, we should be amazed that the language is still pretty cool two decades after the innovation stopped.
I hope the Clojure guys change things. They seem to have the right approach.
Footnote: I was going to be a member of the CLRFI group (roughly equivalent to PEP or SRFI) that got some interest at ILC 2005, and which was going to try to create some sort of forward momentum in the community. It frizzled out, of course, and now http://clrfi.alu.org/ appears to redirect to the ALU homepage.