You don't get it, it happened to .info sites too, so its not just blogger sites or its a huge coincidence that two of my .infos had a dip in traffic for the last 3 days (the lowest for the month) at the same exact time.
I strongly disbelieve that domain extension is an indication of a bad site. It doesn't matter if your domain is .gov, .com or .info. Recent changes in google algorithm must have been the cause for this unusual drop of rankings that many of us experienced whether on blogs or websites, .infos or .coms. Look around about similar topics in the recent three monhts how google rankings dropped for many websites, despite their quality, age or inbound links...
I'm not focusing on google when it comes to my blogspot blogs I do more in community site.But I've also notice that when I'm doing a keyword search on my other site, I didn't see any blogspot domain on every search.
it sucks for people using blogger but i would say that the majority of spam filled websites are on free hosts so i can see the logic behind google's decision