David, I’d have to disagree with you. What you refer to ROI is direct monetary value, which should come immediately following an activity. It’s not that you should stop measuring ROI. You just need to be mindful of other things you can measure. For example:

You went out, and spent $52 to attend an event. You should expect the some kind of return on your money and time investment, and opportunity cost (what other things could you have done with that money, and the time you’ve allocated to attend that event?):

Suppose you had fun. That’s it. Your return on investment of time and money = fun. If that was the initial goal — mission accomplished! or in your MBA language — Positive ROI :)

Another potential measure is the number of business cards / relationships / DB entries (however you want to quantify them) you had at the end of the event. Say your annual goal as a business owner, is to meet 50 new people per annum, which you can nurture and convert to be clients or referral sources. You’ve committed to attend 25 events per year, which should yield at least 2 new people per event. If you woke up the next morning (somewhere. Anywhere!) with 2+ business cards / missed calls /texts, Facebook friends requests or whatever to indicate what actually happened the night before — that’s again — positive ROI.

The return on your investment (time/money) should be articulated prior to the investment. If the goal is achieved — you’re winning. If not — adjust your goals or investments….

Makes sense?