Corporate sustainability is like teen sex.

Everybody talks about it.

Nobody does it very much.

And when they do it, they don't do it very well.

My friend and colleague Joel Makower likes to tell that joke, and it's as good a way as any to introduce Greenbiz.com's third annual State of Green Business report. The wide-ranging report was unveiled yesterday in San Francisco at a conference hosted by Makower. I won't try to summarize it; it's available free for download here, and well worth a read.

Among other things, Makower and his colleagues identify 10 green business trends -- they include radical transparency, green fleets, toxics as strategy, and the rethinking of packaging -- and they measure progress (or the lack thereof) around 20 different metrics, including carbon transparency, carbon reporting, cleantech investments and green power use.

The teen sex joke is fitting because the ratio of of talk to action in the green business arena remains high. Particularly when it comes to climate change -- now and most likely forever the No. 1 environmental issue for business, and for everyone else -- progress has been halting because of the absence of consistent government policy, at the national or global level.

Only 34 percent of the S&P500 companies have promised to reduce their carbon emissions, and some of those commitments have been modest. Greenbiz reports that 37 percent of the reductions were set at 2.5 percent or less, while nearly 15 percent didn't specify a target. That's not going to get us where we need to go. Partly that's because for many companies, the business case for voluntary action is weak.

As a senior writer at Greenbiz, I interviewed Carl Bass, the CEO of Autodesk, and moderated a couple of panels -- one on corporate carbon strategy post-Copenhagen with Christina Page of Yahoo!, Robert Parkhurst of PG&E, Sarah Skikne of The Climate Group and Holly Kaufman of Environment and Enterprise Strategies, another on the intersection of big business and cleantech with Rick Rommel of Best Buy, Kevin Surace of Serious Materials and Lynelle Cameron of Autodesk.

The most surprising moment, at least to me, came when Bass said he was occasionally discouraged by the lack of progress towards a sustainable economy. That morning, he'd said, he was on a platform waiting for the BART train to San Francisco as hundreds of cars flew by. Yep, the CEO of Autodesk, a $2-billion company, takes the subway. This shouldn't be unusual behavior but, trust me, it is.

The carbon management panel uncovered some strategic differences over offsets. Yahoo! dropped its plan to go carbon neutral last summer, choosing instead to focus on energy efficiency in its data centers. Pag said the company didn't think buying offsets was worth the money or commitment of executive time. (I'm summarizing, but that was the bottom line.) By contrast, PG&E has a Climate Smart program that, Robert explained, has signed up 700 customers who want to go carbon neutral despite the murky payoff. Sierra Nevada, for example, decided that buying offsets would score the beer company points with its customers and workers, he said.