I can see the value in your suggestion if we add a few tweaks, Jillaine.
If such a policy were to be implemented, I would recommend we start with a longer period than one year, such as Guest accounts that haven't been accessed for 5 years or more. This would give us a better ability to assess the situation without disrupting more recent signups. We would eventually shorten the period if we determine this situation to be a problem.
After checking the Guest's log in activity, we would then need to send a couple of emails to determine if Guest's email account is still active; if the email account is active, we can then assess if the Guest is still interested in maintaining his/her account (either by his/her reply or lack of response after a reasonable wait period).
Another possible action, if technically feasible and cost efficient, would be to add the ability to exempt the Guest (and Family) accounts from the matches for new accounts.
Finally, we may want to consider a previous suggestion from another discussion of requiring yearly log in by all member levels to keep their accounts in active status.