We have a fairly big team of developers working on a MOSS 2007 implementation. I'm always dubious of everyone using the Site Administrator account in any environment, be it Dev, Test or Prod, to make changes to Master Pages. If something goes wrong, we can't go and ask the person that made the change as multiple people would use the account.
I found a thread online which walks you through giving other Users/Groups access to the Master Pages. This way, if Bob makes a change and something breaks, we can then go and speak to Bob about the change rather than having to ask everyone in the team. Even harder if the team aren't there anymore or if they are on leave etc.
Basically all we did is log in as the Site Administrator and go to Modify All Site Content and select the Master Pages and Layouts link under Galleries. You can also get to this page by going to http://[site-name]/_catalogs/masterpage/Forms/AllItems.aspx also.
This gives you a SharePoint list of all the Master Pages, from which if you go to List Settings page you can then modify the security. Default it is set to just Restricted Read on all authenticated users, and obviously the Site Administrator overrides this to make changes. So we just added our Administrator Group to this which is maintained by our Team Lead.