yes. u can put 2 adsense ads but still total number of ads restriction apply but its not really recommended to do because if site gets banned it may affect both accounts
You are allowed a total of three ad units and three link units on a single page. As long as you don't violate that rule, you can have ads from multiple Adsense accounts on a single page. Read the official Google help: https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=32855 https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=115988 https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=9735
With 3 ad units, 3 link units and 2 adsense search you could have 8 different adsense id on a single page, and that would be ok with adsense.
This forum is a good example of using multiple adsense accounts on single domain. Since it is revenue sharing forum, some percentage of the ads are displayed with the thread starter's adsense ID. So you can see that it works without problems for a long time.
(Just to note that DP only used to be a revenue sharing forum - that program was cancelled a few months ago.)