Facebook has no social plugin to embed wall posts; there is API for it though. It's possible to embed an Activity Feed, but it's just activity of a domain. It's also possible to add a feed from a Facebook Page (could be a business page, etc..).

Twitter has a special widget specifically for this so yes that can be done.

Both of the above can be done with CB Connect, but will require the user to Register or Link their existing account with the various connect sites. Alternative is to for Twitter have a text field for them to supply twitter username then use a delimiter field to format the widget. For Facebook you wouldn't need anything from the user as it's a domain feed and not a user by user feed unless you write a custom solution that's utilizing the API to get their wall feed.