Of course they can! This paper provides a nice overview of the intersection between emerging e-portfolio models (like Elgg, which probably should have warranted more coverage in this context) and social software/networks with learning applications. From the intro:
"It will be argued that through sharing one's digital knowledge artefacts with other learners one not only brings on-line learning in a social context that it is sometimes missing, but also allows new paths of learning with peers to emerge."All the usual suspects are represented here -- Flickr, Furl, del.icio.us, technorati, etc -- in an accessible format. I thought the profile of 43 Things was spot-on and it shows the approach of the paper:
"Short description: A site that provides an area where people can write their goals, become inspired by others and share their process as well as learn from others how to achieve goals.
Social Content: Lists of life goals, desired things to achieve and places that people plan and wish to visit. Also 'have done this' and user profile.
Social Context: Connections are build between people who have listed similar aims or desires in order to have a peer group to support one another. Connections can also be made between people who want to achieve some goal and the ones who have already done that in order to give guidance and support.
Possible Educational implementation: In an educational context writing down educational goals is an important part of planning one's learning path. Peer-support from people with the same goals can help achieve the setting of targets and sharing the experience. The feature 'have done this' would allow learners who have gained certain experiences to act as tutors or help in the scaffolding process.