Creating Keepsakes Magazine says it's safe and gives directions for making the faux wax seals:
http://www.creatingkeepsakes.com/mag...le.899.p4.html
US National Archives and Records says it's not safe to use hot glue. The link to the section is too huge to paste here so go to this site and on the pull-down menu at the top right hand corner select 'Preservation'. On the next page under 'Sections' click on 'Caring for Your Family Archives' then check out the question on mounting.
http://www.archives.gov
Personally, I'd use the faux wax seals (they're so cool!) but make sure they weren't actually touching any photos. The pictures in my scrapbooks are also stored on CDs so I can always redo one should something go horribly wrong down the road. HTH