msafi - 5:49 am on Feb 11, 2011 (gmt 0)
The four values you can pass are category, action, label, and an integer value. Each of these values has an intended purpose and none of them is suitable for a "trigger URI".
To me, events are as good as hit counters -- which are not that useful. Events don't have navigation summary and they don't tell whether the user has returned to your site after triggering the event.
On the other hand, if you use virtual pageviews for affiliate links, you have navigation summary, exit percentage, and you can even see the average time a visitor is spending on the vendor's website because Analytics treats the affiliate link click as if it were a pageview of the vendors site!