Yes. Don't follow users who submit spam, and don't follow users who share spam. If you follow those two rules, it will not show up in your feed.do you have any way to prevent...mmm... "share-rigging"?
"It isn't a problem until it's a problem and when it's a problem you'll be in a much better position to find a solution" Zygar told me that when I was going through endless what ifs the other day. I think it holds true for this situation.
To elaborate— You have the most information about how to solve a problem once it's become a problem. If you're running into scaling issues—you very, very quickly find out where the chief bottleneck lies and can work out a solution. And when spammers slowly try to take over, you'll be able to observe the ways in which they game the system and respond appropriately. Often, the biggest problems are the ones which you can't predict.