You can add the {JFBCLike} tag (or other tags for the different sharing features of other social networks) next to the items in the activity stream. However, please note that sharing buttons are all tied to the URL that the Like/share button is for. That means that there *must* be a unique page/url for each status update.
I don't think that's something you can do with JomSocial. If there's not a unique URL for each post, then the Like buttons would all point to the 'current' page that the activity updates show on, and there's no way for Facebook to know which specific activity stream post was really being Like'd and because of that, it won't work.
I hope that helps explain, but if you need more information on how the sharing features work, just let me know. If you want to test adding the Like button to your updates, please try out the {JFBCLike} tag which you can add in any JomSocial template file. For more information on what files to edit, you'd need to contact the JomSocial developers for advice.
Thanks,
Alex