I too, was sorry to see that Streetlife is transferring to Nextdoor. I've found it useful for disposing of unwanted goods - either sold or given away. However, I'm with Pittcity in that I will reserve judgement for now.
It is meant to be a Community website, and will rely on a good number of members to work - as did Streetlife, I hope it does, but have noticed many SLers cancelling their membership, so only time will tell.
As for privacy - well, plenty is known about you if you use a loyalty card, drive a car, and use a mobile phone - but you don't notice it - so I shall continue to be a part of my local community for the time being.