A method for adjusting a spam index for a blockchain advertiser based on user consensus includes: storing an advertiser profile related to an advertising entity including at least an index value and an identification value; receiving new blocks in a blockchain, each including a block header and blockchain data values, where a plurality of the data values each includes an advertiser identifier, advertisement value, and a recipient identifier; receiving a plurality of spam reports, each associated with one of the data values and including at least one of: the advertisement value included in the respective data value or a reference value generated by hashing the respective data value; determining a ratio of a number of spam reports to number of the data values that includes the advertisement value; and adjusting the index value included in the advertiser profile according to the ratio.