Google has shortened its definition of a widget link scheme by releasing an update, more specific to its Link Schemes Page. It has also clarified the types of links in widgets, which violate the Google Webmaster Guidelines.
Earlier, Google defined widget link schemes as:
Links embedded in widgets that are distributed across various sites, for example: Visitors to this page: 1,472
The new definition however is:
Keyword-rich, hidden or low-quality links embedded in widgets that are distributed across various sites…
It appears that the update is done to eliminate any chance of confusion and leave lesser room for personal interpretation.
In the older definition, it is said that any link in a widget is a scheme. The new definition instead of explicitly saying this provides factors that can be reasons behind Google viewing the widget link as spam.Google Widget Link Schemes Receives an Update!,