I know two people that were investigated, both investigations were warranted in my opinion, but certainly not in theirs. Both times it involved parents that needed help, but would not take it from anyone. One family was living in a van, their kids were not eating well or bathing regularly. They had three kids, five months, two and three. The five month old was drinking formula that her mother was watering down so it could be stretched out. They were not bad people, just very young and very prideful. I understand pride and felt a lot of sympathy for them, but when it reaches the point where you can't feed your baby, pride becomes a luxury that is secondary to your child's health. They did not lose their kids. They were forced to accept help, or they would have lost their kids. That was four years ago and they still have not forgiven the relative (a grandparent) that turned them in and still insist that it was nobody's business.
The second case involved a dad that was spending all their family's money on cocaine and eventually had no food in the house, their electricity turned off, and two children that hadn't gone to school in weeks. They would accept help, but only in the form of cash, which no one was willing to give them. They didn't have their kids taken away either, though the father had to leave the home. Eventually the father got clean and reunited with the family. They eventually forgave the person that turned them in, but of course not CPS.
CPS has also visited them periodically after the father returned, including a visit after their third child was born. If that baby had gone home and the parents not cared for her properly, CPS would have been blamed for that. If there is a fairly recent history of severe problems, they should err on the side of caution.
I think that some people in CPS take their power and lord it over others, just as some cops do, some doctors do, as some teachers do, etc... I think that there is a lot of room for improvement within that system, but I also think that there are some heroic good-hearted people in that field and I know that these two families are better off for the intervention, though they would never admit it.
I have never been investigated and I hope that if that happens I get one of the decent case workers, it just seems to be the luck of the draw, unfortunately. My house is sometimes messy, my toddler is sometimes messy, it could happen. I also think that if someone files a frivolous or untruthful complaint, that the person should be dealt with severely. Held up to public scorn, jail time, you name it.