YANBU
I screen calls all the time and have now trained the kids
. Most of the time any genuine calls, to the landline, will be my Mum. Or the school but they'll leave a message and then call our mobiles straight after. They're all easy to identify, it's the big MUM, DAD, SCHOOL that comes up on the screen 
The rest are sales or courtesy calls. I get quite a few of them, always at the same time, early afternoon or early evening. These days I hate courtesy calls more than sales ones.
Other friends and family tend to text, email, or use my mobile number. Thinking about it, unless they're calling for an immediate request, it's always a text or email.
Recently I've given up ansering the door all the time. Friends and family will tend to call before they pop around, so they'd be expected. Our living room is at the back so I can hide ;) We have a glass window on the door. Sometimes I'll poke my head round into the hall to see if the fuzzy outline (distorted glass) looks like someone I want to talk to. Long gone are the days when I care if they've seen someone in and know they're being ignored.
I'm not unsociable but I am soooo bored of cold calls. Anyone out there who wants me to buy their product, stop cold calls, stop pestering. You go onto my mental list of companies to avoid.
Nearly walked out of friggin PC World the other month. All I wanted to do was buy a netbook and get on with my life. Oh no sales person accompanied me to the tills blathering on about some awful value insurance thing. Said no, that started the pitiful "look I've just been on a Sales course" open quesions. "can I ask you why?". You can but I ain't friggin answering.
PC World you're on my naughty list for several such episodes.