Indiegogo in particular is super sketchy, I did a campaign with them and they had an employee there contacting me and telling me all the shady stuff they can do to help me be successful and if that I can guarantee I'll raise x amount they'll do all these extra things like put it on the front page and in the newsletter and whatnot. They let you extend campaigns forever if you arne't about to hit your goal so you can keep saying "ending soon", then if you do hit your goal, instead of ending, they will let you keep it open to ride the momentum of that, or they will then let you up (or down) the goal and change the date so you can keep catching people who want to just be able to get it, or who want to pile on to a super successful project whose goal is now 1/10 of the original so it looks even more legit. You can also back your own stuff anonymously for as high as you want, so often you'll see campaigns with like $1MM and only like 20 backers and most are anonymous or not listed and you know obviously 20 people couldn't have legitimately backed for that much.
I can't recall a lot of the other stuff you could get away with, including have no proof of concepts and just using renders and being fully funded already and such, but I had to unsubscribe from their emails it was so disgusting. You can tell if you look at their site overtime which kinds of things just stay up forever or how they instantly are over the goal and whatnot. One item stayed up for like 8 months, constantly over the goal.