I'm going to differ with the answers already here, and say no, almost certainly not. If you have any of your systems externally, then allowing unencrypted connections to them might expose eg login IDs that you have an interest in keeping secure, but since we're talking egress filtering I'm guessing you don't have any such systems out there, so by blocking unencrypted services (ftp, pop, imap) you're only protecting other people's secrets, and that's not your job.
Moreover, it's pointless. As long as you allow port 443 outbound - and there would be a riot in any organisation I've ever worked in if that was forbidden - you've got users making SSL-encrypted tunnels out of the building left, right, and centre, and you have no idea what they're passing through them. Could be HTTP, sure, but it could also be SSH, could be IMAP, could be OpenVPN, could be anything at all as long as it's inside that SSL-encrypted tunnel.
So sure, you can annoy people by blocking other ports outbound, but as long as you're allowing HTTPS it's utterly pointless from a security standpoint; it won't prevent a determined adversary for more than a minute, and it'll really annoy all your legitimate users.