I agree with you completely, and I'm so sorry to hear about your miscarriges.
I do think it's really insensitive, and completely pointless. If people want to help raise awareness of breast cancer, which frankly, is the cancer that probably already has the most awareness, then they should donate money or actively do something practical to help.
I have not been upset by this one because thankfully for me I have had heathy babies, but I have seen them about hidden illnesses, diabetes, and autism, to name a few, and I have been in the position of being upset by one of them.
It is very insensitive to randomly post these things when so many people have facebook contacts whose personal lives they know little about. You just never know what anyone else is struggling with at any one time, and people should think a little further than their own computer screen before they post things that are going to remind people how crappy things are for them.
It's all very well to say 'hide it', but sometimes the people posting this tripe often post other nice things, and it's not like they are being malicious, just thoughtless. And by the time you get to hiding it, your heart has already sunk from seeing it in the first place!