I haven't really kept up on what the community is doing when it comes to using certain services.
However, I can say that this issue will probably end up like the age-old picture mail disaster - they'll start blocking PAM access from those who don't have the plan before too long.
I wouldn't be surprised if it happened next month when they reconfigure the service to work with Simply Everything.
I can't say what'll happen for sure, but I can say with absolute certainty that if you don't have a PAM plan on your account, you shouldn't be able to access it, and it's likely they'll catch on eventually.
But either way, might as well enjoy it while it lasts
EDIT: Our department has not been updated on the 5GB data cap. It's news to me. I plan to find out more when I go back into work on Saturday - since they usually let us know about stuff like this well in advance if it actually happening. Also, I forgot to mention, that PAM is only effective for those using the Sprint network... if you're using WiFi, that's not Sprint, and you can always do that at no cost.