Diigo Tests Group Thumbs
I haven’t seen anyone in my immediate circle of social media followers reporting on this, so here is a small update on Diigo, a relatively new social bookmarking site with a lot of features.
Diigo tries enable a lot of ways of using its service and related features. You can use it exactly like del.icio.us to bookmark and tag web sites you may want to search for later. But you can also use it to share interesting bookmarks with your friends, discuss content with like-minded folks, and also leave comments on sites that Diigo users can read later!
The feature they are testing out applies to their groups feature. Now, if you are a member of a particular group in Diigo, you can give certain URLs a thumbs-up if you think it is especially helpful. They are holding off on deploying this feature site-wide until they can make a determination how game-able the feature is.
Groups are similar to a web forum, but centered more around site bookmarks that are collected to provide a resource for the group. There are groups for all sorts of things, from social media to cooking. Some groups are extremely active, and others are simple collection points for related URLs.
This is the group thread that alerted me to the thumbs feature. Here is another article about Diigo where thumbs are mentioned.

