It is a really, really bad practice.
There are many websites requesting access to my contacts when I just want to login or signup. Yes, I understand that you might want to know my contacts to suggest me people I want to follow on your websites. But I just don’t want to trade my precious contacts information for a few people to follows.
It would be much better to just request for my email address for the purpose of login/signup. You can always request for my contacts when I want to discover people on your websites. Blindly request as much information as you want is simply arrogant and unacceptable under my terms.
An average Internet user.