This will very rarely – almost never – happen, and will require a high amount of participation (Metric not yet defined) during the voting process. Key is to make sure that even people in the community that typically don’t involve themselves with voting for proposals, are made aware when a Proposal has been submitted, and that they have been well informed of the issue(s) involved in a factual and unbiased way.
These proposals are the most common and are for allocating funds in the monthly treasury budget. These funds can be used for anything related to support Helium. It may be overhead costs for servers, or Google Apps etc., or it may be for advertising, or to help launch a business that could not be justified otherwise.
These proposals are zero cost and are to make decisions to change the code base (the protocol) of, or the priorities of changes to, the Helium Chain system. If such a decision requires funding, then that funding portion would be a separate Treasury Governance proposal submitted after the Protocol Governance proposal has been accepted. What is unique about Protocol Governance is that the Core Developers can veto such proposals if they are technically impossible, or logistics dictate an order of implementation different that that voted on in the proposal.