I was curious about the same thing, and discovered a few problems:
1. That nice solid bar going straight up/down actually has a lot of gaps in it. I took a snapshot of the tick data on Russel 2K futures on a jobs report. First tick after the announcement was 4 POINTS lower, even though there were no gaps in the 1 minute bar.
2. The brackets get swept a lot in the 30 secs prior to the report -often in the opposite direction of the break.
I think that there is a lot of opportunity to trade the news, but (like anything involving trading) it's not easy.
There are a lot of algo traders who code news reading software into co-located servers, then buy/sell based on the headline number vs. expectations. They will be first in line (and even they will get horrible fills.)
I'm interested to see what other traders think, though. My experience is limited to simulations and looking at the data.