It felt a serious transgression of my privacy. Though in hindsight I realised it was an easy task, I can, after all, see if people are using Whatsapp if I have their number so there is little to stop companies doing the same lookup if they have my number.
But it felt very uncomfortable.
I don't want companies involved with my Whatsapp, it is exclusively for messaging my missus, and group chats with friends and family. Nothing else.
I did read somewhere that one of the founders said the aim was to integrate apps/companies into Whatsapp, but for me "No!".
I am dreading what the ad monetisation will be like. Since everyone I am friends with, related to or worked with use Whatsapp, their market penetration is ubiquitous here in my London ecosphere. Hope they don't ruin that.