AdSense policies section on multiple ad units is ambiguous

[Marcia]

This one, from the Adsense Program Policies (https://www.google.com/adsense/policies)

Up to three ad units may be displayed on each Web site page, but no ad unit shall contain any advertisement in common with any other ad unit. Serving two or more identical ads on a single page constitutes double-serving, which Google does not support.
It's up to Google which ads are served, but while that says it's OK to have up to three ad units on a page, it could be construed to imply that the ad units shouldn't be of the identical format.

[Jenstar]

That section has always been somewhat confusing, but even more so before they allowed multiple ad units earlier this year. It used to imply that you could have multiple ad units, but only if you made sure you didn't run the same ad in different ad units on the page - which was impossible to do at the time :confused:

I have been asked numerous times by publishers if they could run the same size/style of ad unit on the same page, or if all three had to be different sizes. Now I know why I keep getting asked that :p

[Marcia]

Exactly why you keep getting asked, Jen! It needs to be re-written a bit so it's perfectly clear to anyone, which is why I've mentioned it.

I happen to have pages where two different ad "shapes" work well usability-wise, from the perspective of how the pages are laid out and how users' eyes would scan the pages; Yet on others it works best to have two blocks of ads the same. Like on a very narrow page design where there's a considerable amount of scrolling down, it can be better to run all the ads down the side - which means there need to be two skyscrapers.

I look at AdSense as providing additional content for users - so if it's comfortable for them to scan our pages and they scroll down to see what we're offering, having AdSense off to the side gives them an alternative resource. If they're not interested in what we have to offer them, there's a targeted ad right there that may give them just what they're looking for.

That really is unclear in their "help", there's no way to tell what it really means. We don't have any control over the ads themselves, but we do need to know for sure whether it's OK to have two blocks the same or not.

[Jenstar]

but we do need to know for sure whether it's OK to have two blocks the same or not.

Yes, I can say with certainty, that you are allowed to run ad units of the same size on the same page, as long as you don't run more than three total ad units. You can put three skyscrapers stacked, and AdSense won't have any problems with it.