That was the whole point of the DMCA, though. Prevent bad publicity by claiming copyright infringement and companiea have to take down the content before they investigate any response. Any time a company doesn't do that they are risking their own necks. So usually they only ignore it if they know for sure it's bogus which requires that they spend the resources on a person reviewing every notice before the required time expires.
That was the whole point of the DMCA, though. Prevent bad publicity by claiming copyright infringement and companiea have to take down the content before they investigate any response. Any time a company doesn't do that they are risking their own necks. So usually they only ignore it if they know for sure it's bogus which requires that they spend the resources on a person reviewing every notice before the required time expires.