Ok, well let me tell you want really happens when you ignore everything. A guy I know just went through this whole process. You get a request from an attorney to remove some reviews and have the user's info sent over, then you ignore it. About a two weeks later you get another letter, which basically says the same thing. You ignore that too. Then a few weeks later, you get a threatening letter stating that by leaving the libelous reviews up, more damage is being harmed to the client. You press the ignore button and keep on about your day. Then you get some certified mail a month later saying that you're being sued for willfully contributing to the damage caused to the attorneys client because you refuse to take the review down or comply with any requests. You ignore that too. Then you get a discovery subpoena asking for all sorts of documentation about your business and review process, but hey, you've made it this far so why not press the ignore button again? The hearing/trial happens and the client automatically wins because you didn't bother to show up. Then you get a court order demanding the review be pulled down and that you must pay damages and attorney fees. The guy I mentioned earlier ignored that too, and guess where he's at right now? He's in jail for contempt of court with a $50k bond.
Now the legal system might work different where you live, but here in the U.S., that's the way it works.