We have a large mature cherry tree. It produced cherries just fine the first two years we were in this house. We had someone come out and trim the tree the third year (wasn't too happy with their job) and since then it doesn't produce very well. The vast majority of them fall off at an early stage. The ground will be covered with stems and the small beginnings of a cherry. At first I thought it was just shock or something from the year it was trimmed (it wasn't trimmed too heavily) but this is the start of the third year since that happened and they are still dropping.
It may not have anything to do with the trimming, that's just the only thing I can think of that was different since previous years. The tree had also been infected with Western Cherry Fruit Fly (we didn't really notice it until the second year, but it most likely had been like that since long before we moved in to the house).
As you can see, it doesn't look like blossoms, so much as nascent cherries.