I've earned some badges in my Purdue Passport account and in Mozilla.
My Passport ones: http://beta.openbadges.org/share/8c95a6142c3abb0d370677e4bcd65d7e/
These were learning type badges. They have an independent and collective existence. Re. Purdue I felt compelled to complete the set to get off the "compete newbie" level. I don't think anyone told me to do this. Their collective meaning--in my Openbackpack--came from how I decided to group and display them as a collection.
It took me a bit to figure out how to group and display my Open Badges at first--but wasn't completely difficult.
The Purdue Passport badges were very clearly designed in a sequence to lead us through the basic tasks re. interacting with the badge platform first--then how to publish to the Mozilla Backpack second. After these tasks, as an instructor, I have badge development and design badges that took me through the basic tasks and considerations for creating badges.
I think that badges in closed systems have far less opportunities for "attracting others" unless they--like Purdue is doing--are pushed into a more public platform like Mozilla's.