Well let's assume everybody did. Then you would have a coin where all transactions are traceable (except yours, and yours would be the only ones left so...). That's obviously not the goal here, but if everybody wants that, there's nothing you can do. You can't hide a needle without a haystack.
However, it is indeed not good to encourage too much reliance on view keys. That's why, for example, MRL-0004 has an alternate method for auditing of individual transactions that does not involve the broad brush of a view key.
I know you guys aren't aiming to be alphabet proof but perhaps one day in the future it could be a goal and it is concerning because we might imagine that some mass surveillance agency might be able to put together a rather comprehensive database of view keys.
Once the view key has been seen by someone other than yourself, consider the privacy of that address compromised and migrate funds to a secure (private) address. Better yet, never share a view key except for purpose specific, (single use?) addresses. Let them watch a vacant house all they want.
Correct. View key is 1/2 of your private key. It makes sense to share this for specific reasons, but not in general.
fortunately it will probably be rare for people to share their view key anyway. i mean if they are in monero they are in monero for a reason.