I've seen a number of threads in the past few days asking how to notify Google of this or that. I was just playing around with the Google webmaster tools, and noticed a spam report page here: https://www.google.com/webmasters/tools/spamreport?hl=en The notice says that they follow up on all complaints posted. HTH
I don't know if they follow-up on all complaints, many people complain that they report sites and nothing is ever done. I think it depends on the information you provide on how well they can follow-up.
They generally won't reply, the information submitted here is primarily used for them to gather data. They use this data to make alterations to the algo's based on volume and importance of the information submitted. If it's a duplicate or stolen content issue as the title suggests, you will need to submit a DMCA to Google. Download the Google specific DMCA Template here in .Doc format.
They won't entertain all of the reports I guess.. unless you own a big company and lunch report against small blogs/sites, nothings gonna happen.