Daniel Indiviglio suggests taxpayers have discretion over where their funds go. I love this idea. In fact, I considered it a while ago (though I called it "taxpayer earmarks" and was less ambitious than Indiviglio, thinking only a fraction of the tax payment would be available for discretionary spending). I can't find a post about me talking about it, so you'll just have to take me at my word.
I am concerned that the payments are just another form of cheap talk, but more directly destructive. In Indiviglio's example, he increases his share to the DEA from $3.14 to over $160. I think many Americans would applaud that increase despite the efficiency (and ethical) problems of arresting people for enjoying drugs. I'd expect subsidies and make-work jobs to rise, as well, depressing the economy.
You might wonder why politicians don't have to worry about this trade off (pleasing the people at the expense of the economy). Well they do, but its weakened compared to the average taxpayer. If the politician's in charge when the economy sinks, he's (rightly or wrongly) punished for it by losing his job. Moreover, he has business interests (and their campaign contributions) which help keep him in line. But a single taxpayer's virtually unaffected by slightly increasing a subsidy for a feel-good industry. Even if they don't send money that way, most will and that's what makes the difference. It's the cheap talk of voting but without the (and I can't believe I'm wording it this way) rational filter of the politician.