First, friends don’t advertise to friends. So, kind of like not doing business with family. But, we accept recommendations from them all the time. Also, domains are a new form of business. Accordingly, associates may be interested in a website given our influence. But, it depends. Then, app invite is not appropriate personal email. Given, good netiquette to keep your address book private. Then, don’t send advertisements to friends. As a result, it is more like spam since no one asked.
So, email addresses can easily be shared. Also, they are valuable. Next, good friends are extremely valuable. It follows, many sign up forms request access to personal email address books. Then, automatically email your contacts with your permission.
In any event, there are options to skip the sign up step for sending an email to contacts. Given, the address is the contacts personal information. So, it is not polite to share personal information without permission.
Do not share personal email addresses without permission from the contact. Messages within social networks are more discretionary. Social networks provide public profile for viewing. There are privacy settings to control contact.
App Invite Netiquette
Keep address books private because many social networks ask to email contacts, which may annoy them.