I'm a new user and see another reason why it should be possible to upload from the Eye-Fi SD card multiple times: When on a vacation I want to wirelessly upload photos to my iPad and/or iPhone (or Android or whatever) for viewing and backup (have had a camera lost or stolen more than once while on vacation), but I also want to upload everything to my home PC/Mac when my vacation is over. The Eye-Fi card only allows one upload to one host (mobile or PC), and then won't upload to another "host" or even allow manual override or forced upload a second or third time.
I know I can jump through hoops to get all photos into my Pictures folder on the PC/Mac, i.e., transferring from the mobile device, merging, etc. but it is very tedious.
If the Eye-Fi card supported multiple concurrent mobile and PC hosts and treated them independently, then I could upload while travelling and also upload when I get home.