I wrote a bit about the problems inherent in a random Google search a while back and thought I'd revisit this example with Diigo to show the advantage. When you do a random Google search for information on something (i.e. Martin Luther King Jr.) you don't really now the quality of the site before digging beneath the surface of the link. The example below highlights this fact as the links below that came up on the first page of my Google search include martinlutherking.org which is run by the White Supremacist group Storm Front.
The search below is from Diigo where members can click on the Discover tab at the top of the page and then choose Community to search the bookmarks of everyone who uses the service. The list below gives an example from the Martin Luther King Jr. search that was also done on Google. The top sites about Martin Luther King Jr. here are from the Nobel Prize, Stanford University and the King Center which was founded by Coretta Scott King.
So next time you need to research, I encourage you to give Diigo a try.