I suppose it depends on the community.

Here we get maybe 20 to 50 new or re-upped bicycle ads a day, so it is easy to keep up with all the new ads, so I always search "all ads".

Most of the "flippers" walk a fine line between being a business or individual, so I don't really care which side they post on.

I'm not sure about scams and spammers. I haven't posted on Craigslist for a while. One thing, don't set your bar so high that you filter out legitimate buyers. I've had several sellers that were just hard to contact