Sure - but maybe you have ill intent towards others (filing dubious claims, an affair without spousal approval, etc.) and this is to see it happen. It is no different than police doing a stakeout - it is just a private citizen than a public defender.

You can look at it as decreased insurance rates.

If insurance companies could not investigate your insurance would cost 10 times as much.

The marriage investigation is a mixed bag. If you are running a drug running operation I should get the kids and you need some proof to make that claim.