An example of a change to the algorithm would be Google adding a penalty (reduction in SERP score) for companies that try to manipulate Google search by using specific keywords within the URL. To make it clear, having the name of a product or service in a URL will no longer improve the ranking for that product or service. Google has been moving in this direction for some time. It should also be noted, however, that while it no longer boosts the score, Google ranking is not actively reduced by containing the keyword - it just no longer offers the advantages that it used to previously.
So what will having more than one domain name do for me?
If you have more than one domain name, you will primarily be achieving the following:
1. Splitting up your website traffic between however many different domain names you have. This will hurt your SERP scores - making your sites less likely to appear at the top of Google because they will appear less popular.
2. Creating dummy websites that do not rank on Google because they have duplicate data. This factor will kill your quality score - users will simply not be able to find any websites that use duplicate data unless they type in the URL manually.
3. Paying for hosting of domain names and hosting (typically without using them).
4. Possibly being inconsistent with your marketing materials - sending people to different locations. While this may not directly affect sales, it may appear confusing or unprofessional for customers.
What is the best practice for domain names?
The best idea is to have only one true domain name for your business. This will make sure your website ranks as highly as possible on Google and that there is no confusion on the part of customers. It will also reduce your ongoing domain host costs, remove the administrative need for managing multiple domains and ensure best practice for Google - who may penalise multiple domain forwarding in the future.