First post here, and unfortunately its just a complaint about a traffic source that has been very good up until now...
We have been running push traffic from zeropark for months now and have done really well, until mid April.
Quality has seem to go down hill all month long.
Our account rep said they made no changes, and all is good...
Has anyone else experienced the same thing?
Also, another thing I just noticed... With some countries, zeropark won't let you bid below a certain amount per click now... This is a new addition... and if you have any campaigns taking advantage of low bids, don't touch them!
If you make a change to your campaign or do an overall bid change you might get stuck at a new minimum bid.
example: USA has a minimum bid of $0.05 now, used to be $.01
so disappointed with zeropark now...
It was great while it lasted I guess...
Interesting to hear they made the same changes on zeropark as on their DSP.
Minimum bid was .05 and they recently jacked it up 300% to .2
Some of the networks they integrate with, the average bid for the last 30 days has been at or below .2
For example Outbrain last 30 days average bid win is .22
But now the absolute minimum bid is as high as .2
The push ecosystem is "maturing" too, so the overall performance is bound to go down a bit over time. People are getting used to the format, many start to ignore it etc ... it's always the case with any new format. So part of the drop can definitely be related to this. And the increased minimum bids won't help it either.
Anyways, zeropark reps are very active on the forum, so I'm pretty sure we'll see a comment from them soon. 
Hi loudexcursion,
That sucks to hear that you see traffic quality went down, of course, what Matej mentioned earlier is absolutely true, push has been on the market enough time to start being affected by the slight overall performance decrease. However, to tell exactly what were the reasons in your case, we would have to look into your account, see which sources you were buying from and what were your optimization strategies.
Cooperating with your rep on the issue is the key, as we have a full picture and the historical performance of our sources, and can tell you what will work and what will not for certain targeting combinations. Talk to your rep, and I'm sure we will find the solution. You can also write to me here via PM, I'm always glad to help.
As for the minimum bids: true, that was the business decision from our end. If we want to keep up with others in the programmatic environment, our bids have to be competitive, especially in the case of the most popular GEO on the market. In any case, I'm sure we will be able to help you get a positive ROI even with bids that high.
Don't hesitate to contact us when needed!
Hope that helps!
Sasha - Zeropark
Thanks guys...
What you all said backs up the thought in my head... I just didn't want to believe it... LOL

I have found that all networks bring negative ROI unless optimized and for some you need to optimize hard. It'd help more if you bring more context, such as how much you optimized, what offers you promote etc.
There are no profits without optimization.