This reminded me of an idea I had a few years ago: randomly delayed messaging. There should be some utility (Facebook app, whatever) that sends messages that take anywhere from 3 to 7 days.
The idea is that you won't know for sure when the recipient will get the message, so you don't actively expect their response.
Likewise if you get a message, you can reply directly and it will still feel casual, or reply later and nobody will feel ignored.
I have experimented with this, and to my joy, it works. In first attempt at rhythm, I emailed users on a consistent basis. Soon I discovered that they were getting ad-blindness (well, sorta). So now, my new version emails them once every 2, 3, 5, 8, 13, or 21 days, with the probability of a user being emailed weighted over the slower end
l = [1,2,3,5,8,13,21,34] <--- this is the list of fibonacci numbers. The probability of a user being on the track of once every l[7] is higher than the probability of the user being on track for once every l[0].
Users change tracks on a monthly basis. So if you're on a once every 21 day email cycle for June, you might be on a once every 8 day email cycle for July, although the probability is high that you will stay on the once every 21 day cycle
The idea is that you won't know for sure when the recipient will get the message, so you don't actively expect their response.
Likewise if you get a message, you can reply directly and it will still feel casual, or reply later and nobody will feel ignored.