I haven’t used this Flickr’s “People you may know” feature yet. If you’re using Flickr, you will see another box there on the sidebar giving you some contact suggestions. It seems Yahoo! wants to make Flickr more social these days.

As a Flickr user, I can find also find friends based on their data on my “contact page” at another services like Yahoo! Mail, Gmail, Windows Live and also Facebook. Looks nice? Maybe. Flickr will search all contacts that already inserted in the address book. But, it will depends on how I organize my address book, for example in my Yahoo! Mail or Gmail. My Yahoo! Mail assigned for my Flickr account almost has no contacts. It’s simply because I created a Yahoo! account only to signup with Flickr. So, almost nobody in my Yahoo! contact.
What about Gmail? Similar situation I think. Most of my contacts in my Gmail account uses non-Yahoo! email services. So, when I tried to use the search feature, it gave me an empty results. Windows Live and Facebook give the same output I think.