I've HAD external hd's...they were used on my Dell laptop and organized and formatted for that. I've since reformatted the drives, and they work happily with the Mac...I just don't agree/understand how the Mac stores and organizes files via iPhoto or iMovie. I don't trust it.
I've discovered that once the files are in iPhoto or iMovie, its kind of a pain to get them out for sharing. Sure, you can share from within the program, but uploading to Photobucket isn't supported. Therefore, I have to export the file (aka. make ANOTHER copy) to the desktop, then upload through Safari, selecting the file from the desktop. Once uploaded, I have to delete the exported file.
Due to this complexity, or my lack of understanding, I haven't transferred my Gigs of pics over. They're still conveniently organized on my hd's and accessible by any program and browser. I just wish iPhoto and iMovie could reference those locations without modifying or copying the original.