Are legal issues normal in Porn?

I am planning to start a porn site with scraped pictures from tumblr. I also plan to respond and comply to any DMCA notices and image removal requests. What I am afraid of however is getting sued. So my question is: is it common for copyright holders to take legal actions against porn pictures that are floating around everywhere?

As far as i've heard the bulk of complaints will ask you take down a picture asap, which if you comply you can avoid any problems all together. I think if you use "amateurs" then you won't run into nearly as often.

That's great to hear. However, shouldn't scraped content from Tumblr be safe? If the copyright holders wanted to complain, wouldn't they have taken it down already from Tumblr in the first place?