There is NO WAY that spam will ever be personalized enough to make it become priority mail
I think it could be. The baselines for creepiness in our interactions with machines is something that continually moves. I know a few older folks who find it creepy that their mobile phone knows when they've arrived at a certain location and can alert them to some reminder. Speaking to an 'assistant' program running on a phone is currently creepy (or just odd) to many people, but I bet in 5 years it will be absolutely normal behavior for 30 year olds.
The more comprehensive personal data collection becomes the better targeted spam will be, it is just a matter of applying some good predictive algorithms.
A friend texted me a bit ago about wanting to go to a certain taco shop for lunch. It may seem random, but I bet if looked hard enough at enough data his cravings for that taco shop are not random and could be modeled. So if he is sitting around one day around 10AM, which is when he normally thinks about where to go for lunch, and his phone showed him an ad for a different taco shop, that would be a nearly perfect time for that shop to advertise to him and he might actually appreciate the suggestion. That might seem creepy right now, maybe even in the next 5, but it isn't all that bug a step from saying "I want a taco" to your phone and getting the same recommendation.