Thanks a lot for flagging this 
I totally hear you.
When we started with the idea of the contact list we didn’t worry too much about this since, at that time, most of people had zero, one or two contacts in Monzo. So, yeah, it was one of those “let’s not worry about it until it becomes a problem”. And here we are, this is a problem now 
There are a few ways we can solve it. I think the right solution would be around giving more importance to contacts that you’ve interacted with before or contacts that are around you or closer on your network… things like that so we don’t really need to ask you to manually “hide” people but we get to do it in a smart way. But I don’t know yet, we’ll think about it and try to give a nice solution so you don’t need to see your professional contacts crossing the frontier of your personal life 