Exporting from at least some smart groups exports too many records. This can be replicated in the Drupal demo system running CRM 1.6.8124. Here's how:
1) Do an advanced search for record type "individual" and memberships "new" or "current".
2) Create a smart group from the search results. I have done this in the demo system, creating the group "az-test".
3) Click "Manage Groups" and then on "Members" for the smart group. As of now, doing this for az-test produces 11 records.
4) Select the "all 11 records" radio button, "Export Contacts" from the "more actions" menu, and click Go.
5) Select the "Select fields for export" radio button" and click Continue
6) I have been testing with just three fields: individual first name, individual last name, and individual email home. For convenience, I have saved this mapping as "az-test". Select or recreate this mapping and click Export.
You will get way too many records, virtually all in the database, although the early screens in the export wizard confirm that only 11 records will be exported.
I am attaching a sample export file.