Yes, this code is open to exceeding the Governor limits. It should only be used where you know it will not be triggered in bulk.

For example, if you’re just checking whether an end-user has updated some fields, it should be safe. However, if it can be triggered via, say, a bulk load via the Data Loader then you’ll need to code as few DML statements (eg SELECT, UPDATE) as possible — this takes a bit of thought, but can typically be done by loading lists and manipulating them in memory.

Using your example above, I wrote a trigger to pull the Primary Contact information from the Related Contact list to the Contract. I was able to build a trigger that brings the Primary Contact ID onto the Contract from the Related Contact Object (using both the ContactID as part of a WIL for a custom email button – also need to pull the Contact Name for use in an email template – but that’s another issue)

I posted a question about using the ContactID populated from the trigger and another community member commented that I will run into Governor limits because the Select statement is in the For Loop. Your trigger above has that same format – how did you approach the Governor limits issue?

As to updating a field on a Contact when an Opportunity is won, I would recommend directing your question to the Force.com Discussion Boards. Please provide an explanation of what you are trying to accomplish, and please also explain WHY, since there might be a better way to achieve your goal.

Ha, it’s amazing how the universe works sometimes!