Adsense and Entrecard are not a Problem together just as long as you are not showing the 125×125 Adsense Ad unit. However you should also know that When Placing your Entrecard you should not Try to Trick Visitors into Clicking Ads and here is an Example of what I have seen Today someone placing a 125 Image only Adsense Ad Directly under the Entrecard sounds like a good Idea.
But what Happens when People Click the Wrong Widget these people are Causing Invalid Clicks all the Time and Costing Advertisers Much money that is Why Adsense Earnings are Dropping all of the Time They Should Be Reported for this Simple reason that they are the Reason why Publishers are Getting only a Few cents per Click.
If publishers want to make More with Adsense then they should work together in getting rid of all the cheats in the system entrecard Visitors are all banner blind and do not care about Ads and why should they be tricked into it.
What you should expect from Entrecard Visitors is Regular Visitors and Maybe Sometimes Comments but do not Expect to Make money from Entrecard Traffic but there could be many reasons why. It is quite a good system actually to use as a Guide to See who does things Right and Wrong you can Learn much from reading blogs from Advancing blogs maybe much more than you can from the A-listers because Advancing bloggers Make Mistakes that you can Spot and Learn from while the A-listers only tell you how to do things perfect.
Use entrecard and Adgitize to Build Blogging Relationships,Increase Alexa Ranking find related Blogs and get some comments but not try to trick Entrecard Droppers and try to cause Invalid Clicks.
The Owner of the Site where I seen this has not yet being Reported because I am Giving them Time to Move the Unit away from the Entrecard as entrecard is a community also but I hope they are Quick because the Next Click they Get could Look like this Image Below and a Very disappointing Email From the Adsense Team