Notice that, as you might expect, the concern generated by "big labor" is roughly commensurate with organized labor's declining influence in the private sector over the last 45 years. And concern about "big business" stays pretty consistently in the mid-to-low 20s except for spikes during the recessions of 1979, 2001 and 2008. That strikes me as a decent proxy for the success liberals have had over the years convincing Americans that big business wields too much political influence. They've never been able to hold the ground they gained during recessions.
The upward slope of the distrust of "big government" line, however, is pretty constant. It spiked more upward still during the Johnson administration and drastically downward only with the rally-around-the-flag effect of 9/11 and the anti-Wall Street backlash provoked by the 2008 financial crisis. If you're a liberal, it's a depressing fact that the upward slope of the "big business" line remains pretty constant throughout the Carter and Clinton presidencies. It's even more depressing that it slopes even more sharply upward than the historic trend line throughout the Obama presidency. And, if all that weren't bad enough, Gallup's partisan breakout of the sample reveals that, between 2009 and 2011, the number of Democrats who viewed "big government" as the gravest threat to the country rose from 32 to 48%, while only 42% of 2011 Democrats identify "big business" as the gravest threat.
Taking all this in, you have to wonder whether Democrats know what they're doing by positioning themselves unabashedly as the party of activist government in the run-up to 2012.