That's a good question. (For others: Tom is asking whether you should mark all suggested matches as Rejected Matches if you're not going to propose merges.)
I don't really have an answer.
I would say that it's a good idea to reject all matches that don't represent the same people, but I have two reservations about doing this:
First, we're always improving our matching system. This means that while they may come up as suggested matches today, if they really don't look alike, they may not tomorrow, so it's unnecessary to make them as Rejected Matches.
Second, Rejected Matches are recorded in Activity Feeds. We plan on removing these, and only leaving them in when someone is rejecting a proposed merge. Until we do that, rejecting matches that look nothing alike crowds the feeds.
Personally, if two profiles are easily confused, I mark them as Rejected Matches. Otherwise I don't do it consistently.