Let's do a test and find out which search engine does best, Google vs. Bing. 

Go to Presari and enter the word: 

cancer

Now look at the number of pages in the results:

Google  - 222,000,000   

Bing - 120,000,000 

Very clearly, Google has indexed a lot more than Bing. 

Now enter the words:

cancer -.com

And look at the number of pages in the results:

Google  - 11,600,000 

Bing - 115,000,000 

Google responds well to the monis dot com command. Bing does not.  

What to do? 

How about we tell the search engines to also look for just one tpe of trustorthy type of domain source? 

Enter the words:

cancer -.com +.org

Now look at the number of pages in the results:

Google  - 81,400 

Bing - 156,000 

The first ten Google pages show no .coms. There are a few .coms on the Bing pages. 

We can try entering the words:  

cancer -.com +.edu 

Now look at the number of pages in the results:

Google  - 24,300 

Bing - 531,000 

This too shows a pattern where Google has no .com, and Bing lets a few in on each page, as well as a few .govs and .nets.

Now let's try one more. We can enter the keywords:

cancer -.com +.gov 

One more look at the number of pages in the results:

Google  - 14,000 

Bing - 509,000 

The first 100 results in Google are all .gov's. 

Bing brings in very few .govs and brings in a mix of .coms, .orgs, and .nets. 

Conclusion: At least with these words in this test, Google gets better results. In order to achieve clean results using The Minus Dot Com, it is necessary to add a second keyword command.