Will Wilkinson opines about the enormity of Obama's budget and how the average American cannot comprehend hos much money $3.5 Trillion is. He doesn't help, because he doesn't want people to comprehend it, he just wants it smaller.
The NYTimes blog Economix similarly notes the difficulty in comprehension of the number trillion, without really helping either.
A trillion is a large number - 1,000,000,000,000, 1E12. The answer to the economix question is there are a million millions in a trillion, but how important is that?
There are two key elements to this. First, these commenters have the opportunity to clear up the confusion and help people grasp the concept of a trillion. $3.5 Trillion amounts to a little less than $12k per person. $12k per person is a number people can understand. Breaking numbers down make them easier for everyone to understand - you'll not often see a scientist or engineer write twelve zeros out, but scientific notation makes it easier to comprehend and use the number.
The other element is George Bush's 2008 expenditures were $2,983 Billion, or could be rounded to $3 Trillion. Why didn't people care about how big a $3 Trillion spending plan was, but now a $3.5 Trillion plan warrants such closer scrutiny? For that matter, the federal outlays topped $1 Trillion in 1987!
The increase in spending is needed and is a rational response to the collapsing economy and deflation. Explaining things how people can understand them helps build support for that spending, and I think focusing on people's confusion is a deliberate effort to undermine the stimulus policy.