I did most of these analyses of some of my competitors for “freelance SEO / PPC” type phrases + location type phrases on google.co.uk late last year but never published them. It doesn't look like a great deal changed over the past year...
In summary, Google results even after the major Google updates of 2011-12 aka ‘Panda‘ and ‘Penguin‘ still contain a fair serving of ('black hat') SEO spam. This includes:
In no particular order here is what some current competitors of mine are up to in Google.co.uk non-paid results . I have anonymised the details (including the search queries in question).
I live on the Surrey / Hants border and focus on London as a target market. I do not have a London business address (and neither do 2/2 = 100% of my competitors listed in the Google Map section of search results for some phrases relating to the London area).
This entity is listed at time of writing on the Google Map with the following address (which I anonymised):
[1 The Street],
[Town 30+ miles from London]
Central London Post Code
This listing ranks on the Map section of search results for some London-related key phrases.
This entity is listed on the Google Map at time of writing for some searches with a location of (what appears to be a hidden full address) of “London” only which isn't marked on the map. This appears to be in the same area as their previous address listed on the map which was a mailbox. Google Map guidlelines state that a mailbox located at a remote location or a PO Box are not acceptable business addresses.
This entity appears to be using blog comment spam software as well an (illegal) Russian link building service which involves hacking sites to get links!
This agency relaunched under a new domain a while back - view ranking data for their old domain below. Notice a drop around April 2012?
April 2012 was when Google launched their Penguin update, aimed at decreasing search engine rankings of websites that violate Google's Webmaster Guidelines by using now black-hat SEO techniques involved in increasing artificially the ranking of a webpage by manipulating the number of links from 3rd party sites pointing to the page.
The above data is on the number of phrases the site was ranking for on google.co.uk according to semrush.com. The semrush UK database contains 12m phrases in 2016.
One of their directors has recently written a book on SEO....
Many at time of writing appear to have a lot of paid links. One (a .co.uk site) has a page containing poor English / gibberish is ranking for core key phrases related to a UK City but mentions a region of California on the page ranking for at least one of these phrases alongside multiple other pages!
Some are still using doorway pages (i.e. substantially similar websites owned by one entity) successfully at time of writing (after the update designed to address this issue: http://googlewebmastercentral.blogspot.co.uk/2015/03/an-update-on-doorway-pages.html)