Ask HN: Is this a feature or bug in Google Docs?

Playing around with Google Docs and I noticed when I use the 'invite to share' option and type in an email address GDocs updates the email address to include the accounts first and last name.

To see if I could 'abuse' this I used a random word generator + excel to generate a large number of likely email addresses. I then pasted these randomly generated email addresses into an 'invite to share'. This then updates the emails to confirm if the email addresses match an account + provided the persons first/last name in the majority of addresses that were confirmed. I Googled some of these random emails and could not find the names publicly available against that email address, so it seems Google is offering information the person has not chosen to share.

I contacted Google with this as a bug. They responded this is a feature and not a problem. I feel this is sharing of private information and should not be allowed if the names are not in the invitees contact list. Further spammers could use this confirm randomly generated email address and help them avoid detection via sending purely randomly generating email addresses, whilst including the persons name in emails to assist getting people to trust the email.

I don't agree this this should happen, and may even cross data sharing law in some countries (I'm no lawyer/expert here). I wanted to ask the folks at HN and get their views if peeps think this is reasonable or not?