Source: Google Quality Rater Guidelines
Google keeps spam deliberately in the index because its "respects the query as written", e.g. a search for brand.tld although the correct domain would be thebrand.tld
Google should respect quotes. Or emailadresses. Or at least emailadresses in quotes.
I don't respect Google for being as intelligent as you need to be to keep spam deliberately in the index.
Something to discuss about:
To what extend is this Google policy raising the value of keyword domains for spam purposes?
How will this Google policy effect the SERP quality?