Yeah, it ws probably the same reason for me. It was when first Kindle Fire was released.
Some sites/store numbers seem to be out to me too, to my experience the Google Play and Amazon seem to be correct. I wanted to see for sure so put a Google Analytics “event” message in my app to tell me when a user runs the app the first time telling me which store it was downloaded from.
SlideMe says 4,603 downloads (over 2 months) for my app but I know the real number is approx 580. Arrow Mania (Free) 1.23 for Android.
Opera says 14,900 downloads (over 2 months) but real number is approx 790. Arrow Mania (Free) 1.23 for Android.
For comparison Google Play installs are about 3000 a month, Amazon normally 400 a month (except something happened this weekend on Amazon and looks like it is taking over past Google now, great for me!).
Google Play + Amazon + Opera + SlideMe still get good “real” download numbers though, I’ll be uploading my next app to all of them too. Plus you never know when you might get featured or someone finds your app on one of the other sites and then downloads from Google.
Disclaimer:
My experience and numbers above should not be taken as fact. For all I know it could be my app doesn’t install+run from these sites/stores for some reason (I’ve been looking into this, no joy so far). But there could be something wrong with my APK for example. The above statement is therefore speculative and research in progress. Hopefully more firm answers to some or all of this subject can be found.