To make Widgets Successful

http://www.imediaconnection.com/content/18419.asp

Policing:
....many of the successful widget platforms provide feedback mechanisms where the community at large can comment and vote on widgets, such that the crummy ones get buried and the great ones are given top billing. They also build in reporting mechanisms so that bugs or malicious code can be quickly discovered and removed.
Without a system for self-policing, widget platforms are doomed to repeat many of the same mistakes as email.

Standards
Bill of Rights that contains some basics, such as the notion that when a user tells a widget to uninstall itself, the widget should do so. Another might state that widgets can't use contact information without permission. Much like email, widgets could soon become things people want to protect themselves from, rather than engage with.

Prioritizing messaging above utility
The best widgets extend utility to the people that install them. Messaging is a secondary concern, if a concern at all. If marketers fail to realize this, we could flood widget directories with thousands of useless widgets, killing off the widget ecosystem.

Crummy success metrics
Viral pass-along can be one of the measures that marketers look at in order to gauge the health of the campaign, but if that metric is overemphasized, designers will start designing to fulfill on the metric, delivering "success" at the expense of compelling utility. No tricks to get users to send it along!