SEO Turning into SEM ?

I’ve noticed a trend lately. SEO companies are using SEM to describe their business more and more. Most new companies are launching as SEM companies and saying very little about their SEO services.
What’s the difference?
Wikipedia defines SEO Search Engine Optimization as…

Quote:

Search engine optimization (SEO) is the process of improving the volume or quality of traffic to a web site or a web page (such as a blog) from search engines via "natural" or un-paid ("organic" or "algorithmic") search results as opposed to other forms of search engine marketing ("SEM") which may deal with paid inclusion.

Notice how SEM is even mentioned now in definitions of SEO
Wikipedia defines SEM Search Engine Marketing as…

Quote:

SEM, is a form of Internet marketing that seeks to promote websites by increasing their visibility in search engine result pages (SERPs) through the use of search engine optimization, paid placement, contextual advertising, and paid inclusion.

So […]

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