I encounter that obsession quite a bit (I guess I hang out at the wrong water coolers), and I think these people should use it as a yardstick of "success" because (most of; but see below) the people who don't pay Federal Income Tax are desperately poor (75% of them make less than $30k/yr). So: the higher the percentage, the "better job" the 1% must be doing at pushing the middle class into poverty. Yay.
The Law Of Large Numbers says that some of the returns that have a $0 income tax bill are for those making over $1M in income, but usually there's an extenuating circumstance[*]. AFAIK, the largest *growth* in these non-taxed filings is in the $75-$100k/yr income group, mostly due to having a few kids and a (soul-, pocketbook-) crushing mortgage. 20 years ago, it was 99% low-income = no taxes.
/jordan
[*] Remember when Hillary Clinton's book came out? The sales of it pushed the Clintons over $1M (including POTUS Bill's $400k), but they gave 100% of the income to charity and thus actually paid slightly less than an "ordinary" $400k income person would have.