Not being able to stop people from using a permissionless system is beautiful, isn't it? but I bet many don't enjoy it when that freedom is exercised extensively. Luckily we are in a crypto-economic system that can protect itself by setting the right incentives ;)
Take the Wish For Change track for example, for a small fee+deposit it allows anyone to post a remark on-chain, e.g. I use it in the way I understand it should be used, to gather community sentiment about actionable ideas/changes that normally require some level of privilege(e.g. modifying the runtime), changes that I'm convinced can be beneficial for the general community and that I know me or my team can deliver without relying on a third-par(i)ty. Other people might see it as a good avenue to give exposure to an idea or arbitrary post as said remarks are made visible enough by the governance platforms many people frequent on daily basis.
If you think that a referendum is spam, pallet referenda has some protection mechanisms like the referendum killer that can slash decision deposits(no useful if there is no DD) but if you want to prevent spam earlier then there is the submission deposit that can be raised to a high enough minimum to prevent abuse. What would a good minimum be?
it' worth noting that the current implementation uses the same SD for all tracks, if it's too high we would be making OpenGov less open.
Other considerations:
collect_deposit that sends the submission deposits that are locked forever to a configured account like the Dark Hole's event horizon ;)