I get annoyed when 'friends' do this. My daughter's Scout Leader sends Newsletters with everyone's email addresses in the 'To:' field. This breaches the Data Protection Act. Some of these email addresses were children's!
Protect children and friend's email addresses by simply putting them into the 'BCC:' field. Stands for 'Blind Carbon Copy'. Every one gets the email BUT, they only see their own email address.
SAFE!
Yes, all email programs have a 'BCC:' field.
I know this is all a bit inconvenient but, it is a solution.