Try reading the AdSense Policies:
[support.google.com...]

Product-specific policies

AdSense for content: Publishers may place up to three AdSense for Content ad units on each page. Out of those three ad units, no more than one can be size 300x600. Publishers can place more than one of all ad sizes except the 300x600 on each page. In addition to three AdSense for Content ad units, publishers may also place up to three link units and two search boxes on each page. These policies apply to both desktop and high-end mobile optimized sites.

If you don't know what the rules are you're going to have a short-lived ride with AdSense as they cancel accounts for many reasons.

Not following the rules, especially if you haven't read them and don't know what they are, is usually the first step to being banned.

Please read the policies before proceeding.

Thank you. Most I ever tried was four, and most pages have two.

You can run four ad units per page if you run them through dfp and have them compete against another ad network. If Adsense beats the other ad network in terms of rpm, then there will be times that 4 adsense units show on a page.

Try explaining it to AdSense support after they terminate your account for violating the policies. Best we can tell, based on previous posts, they largely ignore people after being banned so enjoy those 4 ads until the shoe drops.

Whether you have a trick to make 4 ads display or not really doesn't matter after they pull the plug.

It's the Golden Goose laying Golden Eggs problem all over again.

Dfp isn't a trick, and I have emails from both adsense people and dfp people saying it is all right to do it if no hardcoding, etc. is involved. I have also attended Adsense in the City events where we were told 4 ad units run through dfp, if done correctly, is okay. Having said that, I do not run 4 ad units per page.

I didn't say DFP was a problem, but they said 4 ads are OK?

they said 4 ads are OK?

Yes. I've asked that specifically the last two times I've talked with them. Two adsense units can be hard coded, but at least the 3rd and 4th have to run through dfp and at least one has to compete with another ad network.

I can verify what ember is saying as I have been told the same thing by AdSense reps at two different AdSense in the City events. They encourage people to use DFP and to have AdSense compete against other ads. I personally don't use it because it's just too complicated when compared to AdSense alone and I really don't want to spend the time figuring out how to use DFP.