If all of the content is squeezed into one page, like the example, the page won't rank well for anything (baring off page optimization).
Google keeps track of how many times users click 'back' from a search result to a search page. Needless to say it's going lower the subsequent rankings that the dentist page receives.
Decreasing the number of pages through clever AJAX use can improve user experience. But it still makes sense to have different chunks of content on different pages, linked together. The SEO implications are a reflection of this.
One of the commenters made a good point that he had to navigate too much to see the phone number. IMO, the phone number, address, and a link to a map should be on the screen at all times (using CSS fixed positioning).
Having accurate information in local directories would be considered "off-site" factors. Off-site factors are very very important, but does not negate the importance of proper on-page SEO.
And yes, for a website like the example, I think the contact info should always be very easy to find near the top of the page.
"There definitely can be some negative SEO effects..."
A one pager, in my opinion, can be great for a small business.
You would definitely need to provide the user with conventions they are used to such as (contrary to DECH's blog post) providing pseudo-navigation at the top of each section.
Of course none of this matters if you aren't putting in any effort to convert that user into a possible customer. So a few things to include:
- scrolling contact info
- contact form
In the end the user get's "faster page loads", and therefore more gratification from using the website.
Disclaimer: This was just a stream of thought, I do not encourage or discourage one pagers for any given case.
2. The more content you squeeze onto one page, which could be spread across multiple pages, means the keyword density will be lower.
3. The page will not rank as well as it could have. It's basic SEO. Maybe dentistry isn't a very competitive niche and you can get away with a lower keyword density in the body text.
2. True, but see my first point.
3. True, BUT only in a competitive market. In my original comment I said "...can be great for a small business.", I probably should have used the words "local small business".
Because ranking for something like... "Miami Electricians" or "New York City Dog Sitters" would be easy and would be most effective (in my opinion) with a one page site.
Here are queries I tried: 1. "parkside dental" 2. "parkside dental goldsworth"
I found it with the second query, it's the third result.