Google said, “Currently, we investigate every spam report from a registered user. Spam reports to the unauthenticated form are assessed in terms of impact, and a large fraction of those are reviewed as well.”
A comment on WebmasterWorld thread states, "Google had repeatedly said that they looked all bad search results reports
And they just said it again.”
Another one says, “I have been thinking this for quite some time as I have reported a site hidding text etc for months and it has risen in the serps and not dropped. I also feel all this sudden losing key terms is the act of this so called panel and not the algo so now I fear we are at the mercy of rouge panelist who may know nothing about a site structure but just like what the stupid thing looks like.”
Do check out the thread to know more about the critical comments Google received for its post, An update on spam reporting.