I have seen similar stats that range G from 60-90+%, Y from 6-28%, MSN/L from 1-16%, the differences probably due to the niches and demographics involved. That does nothing to alter her two main points:
This is when you realize that no matter how hard you might want to break away from Google, you see just how ridiculous that concept is. Unless you get lots of traffic from places other than search (which is always nice), Google has to play a large part in your traffic strategy - like it or not.
1. "Google has to play a large part in your traffic strategy".
When optimising for search Google has become the default. One can survive on Google alone and even prosper. However, that additional 16-17% (her numbers) of seach traffic could be the difference mere surviving and a comfortable living - an additional 20% potential revenue is well worth pursuing...even for rich folk.
There is also the conversion factor: not all traffic from all sources to all niches converts equally. It is quite possible, for example, for Yahoo traffic to provide the same actual number of conversions as a much greater volume from Google.
You need to know your numbers.
2. "traffic from places other than search"
This is the big black hole in the floor that everyone walks around while pretending it doesn't exist. Yet this 'alternate' traffic is often the best converting traffic by a logarithmic factor. Yet 'search' is king. There are none so blind as those who will not see.
There is an increasing awareness of social media as an alternative traffic source, primarily because some in the SEO community (and others who view SEO as passť) are pushing SMM hard. There is much less of an understanding of it's actual value, often a deliberate obfuscation. Shout traffic volume, praise traffic volume, hurrah for sheer volume; it's easy to generate, looks great in reports, impresses the clients; conversion rate and ROI are so Web 1.0.
The 'ancient' alternative of direct type-in/bookmark traffic is still the best converting category. Why do you think domainers buy as they do? Leveraging type-in errors is one big reason. We hear more and more about type-in and domain squatting and less and less about type-in as valuable for all sites. Hurrah for the tabloid bloggartsphere. Those who come direct to you are pure gold. Woo them well.
The 'original', 'before Google', indeed 'before search' and still critical traffic source is the backlink. Unless it is of the PR-chasing junkbond variety. Like traffic volume, pure link volume is easy to generate but an exceedingly short term outlook. A quality backlink provides highly converting traffic. A high quality backlink supplies high volume highly converting traffic. That it also juices PR is a nice added feature.
To put all your livelihood on one number, on one supplier, on one client, is a inherently hazardous choice. Make your own risk assessment, your own business plan, and proceed...