I've been a Becki my whole life. Nothing wrong with it as a nickname. The Beyonce crap doesn't bother me. My hair is amazing.
When I see people referred to as "Becky" on Twitter for the crime of being of a certain race/class/role, I just laugh and decide I will defend my name.
Rebecca is a great name and I don't think it dates as badly as some other names, none of which I will mention as I've realised how crap it is to see random strangers hating on your name.