I just noticed a short bit in Terry Brock's excellent Achieve Your Success blog, in which he quotes Andrew Palmer, saying "Money Loves Speed". This is so true, especially in marketing, but equally in other facets of business.
The reason for this is twofold: first, speed assures that there is a tighter feedback loop between planning and execution (think shooting the rapids vs. drifting lazily down a river). Second, speed reduces the "t" component in time value of money calculations - and since those express value as (1+r) raised to the power of t, you get a geometric payback!
I've been using this recently by tightening up the timing of my marketing cycle for our Simplified Strategic Planning seminars...we used to begin advertising analysis nearly two years from the date of the program, and we are constantly looking to shave days off of the cycle. Web marketing is one of the best "fast cycle: marketing approaches you can use - because you can usually assess a campaign in a matter of days rather than weeks.