Direct democracy is nice in theory, but outside the United States seems to act effectively only at small-scale levels. Two cantons in Switzerland do it, and that's all.

My objections to it are largely these. The first, explained by James Madison, in the Federalist number 10:

(A) pure democracy, by which I mean a society consisting of a small number of citizens, who assemble and administer the government in person, can admit no cure for the mischiefs of faction. A common passion or interest will be felt by a majority, and there is nothing to check the inducements to sacrifice the weaker party. Hence it is, that democracies have ever been found incompatible with personal security or the rights of property; and have, in general, been as short in their lives as they have been violent in their deaths.

The others are summed up by democratic theorists as participation, deliberation, and equality, which can be explained mostly as 'y'all aren't going to participate, act like nice rational folks, and let everyone be heard'.

EDIT: And I guess with regard to voting or not voting, I see the dilemma (which I don't have, I vote as often as I can) as this: do you care more about a goal that you don't even do anything for by not voting and staying put and which would probably be more effectively realized by actively mobilizing, speaking up, and calling for a change in the nature of representation (and which is, according to said democratic theorists, probably pretty infeasible in practice for both human behavioral and bureaucratic reasons if you want to accomplish anything within a reasonable amount of time), or do you care more about using this clearly very imperfect system to accomplish other goals you may have for society, which are far more likely to be accomplished if people do in fact vote for them instead of sitting home and doing nothing?