I run this on my forms. I include a hard to follow disclaimer that says your entries are saved in real time "for your convenience"

It freaks people out when we reach out on the partial fill, but since I sell lead generation, it's a nice trick that they appreciate.

It's definitely problematic.

Luckily, our time is costly so only one single follow up occurs ..no list selling, mailing lists or repeat calls occur, but would be easy to do.

Its actually just an available feature on existing form software