Not being a recruiter from what I know around the industry.
Banner towing
Traffic watch
pipeline patrol
aerial mapping
Those four are not highly regarded but are also certainly not discounted. All things considered equal you are likely to lose a spot to someone who was a CFI or flew part 135 single pilot if all you have are the above times.
As for being blacklisted..as a timebuilder that is difficult.
Crossing a picket line is not likely to happen while you are building time.
If you are a aviation harlot and fly for free in a position that is normally paid that is highly looked down upon. With the last scenario it would not blacklist you though because all they would see is SIC time in say a citation or king air 350. They would not know that you flew as a required crew member for free when that position should have been filled by a paid professional.
As I said, this is only what I know from a few conversations with our recruiters.