1. I tend to call myself a "radical libertarian" as well. I prefer that to "anarchist" or "market anarchist" or even "anarcho-capitalist" for two reasons. One has to do with the rhetorical problems the anarchist label raises, but the other is that whether or not I'm an anarchist depends upon my mood that day. More seriously, I don't think the case for anarchism is completely convincing. My disposition is to accept it but I'm not completely convinced enough to use that label (rhetorical problems aside). Understand, of course, that I think the set of issues where government might be justified is pretty small, hence my comfort with "radical libertarian." The fact that I see myself as a person of the left who happens to believe that markets and other voluntary institutions are the best means to the left's ends also makes me comfortable with the "radical" label. (Having been called a "PC libertarian" and a "neo-conservative," not to mention a fraud and a liar, in the last 48 hours, labels are kind of fun these days.)
2. In my "Comparative Economic Institutions" course, I spend part of a very early class day explaining why I will NOT use the terms "capitalism" and "socialism" in that class (a promise I keep to a large degree). My reasoning is Hayek's - the terms were both invented by those sympathetic to socialism. Moreover, the very terms bias the debate. To add some more meat to Chris's argument, look at the words themselves. "Capitalism" suggests a "belief in capital" and it puts capital as the central organizing principle around which the system is built, or at least around which "the goods are delivered." By contrast, "socialism" suggest a "belief in society as a whole" and puts society as the central organizing principle or recipient of the benefits in that system. I would suggest that both implications are incorrect (i.e., capitalism [truly free markets] doesn't primarily benefit capitalists, and socialism benefits the few at the expense of the many).
More important, though, is that neither term speaks to the institutional arrangements that each system requires. Thus, I prefer the language of "markets" and "planning" to "capitalism" and "socialism." Although these are not without their problems, they have the advantage of allowing us to talk about how social coordination will take place in each system and what varieties of arrangements those fundamental coordination processes might produce. For example, we can talk about markets in which there is worker ownership or not. And with planning, we can talk about the differences between, and challenges facing, democratic planning institutions versus more centralized, autocratic ones. This dichotomy forces us to ask questions about how social coordination takes place and what sorts of institutions forward it. It should lead us to ask "how do/would markets work?" and "how does/would planning work?"
It also gives us room to talk about real world systems as being neither purely markets nor purely planning, and to explore whether the coordination processes can be combined, or whether one will tend to crowd out the other (or at least cause unintended undesirable consequences) when they are significantly mixed. It provides an institutional analytic framework for doing applied work, including exploring economic history.
In any case, Chris's post is right on, both as a question of how to talk to the Left and as a really serious question of how libertarians understand our own worldview.