I rate most of them. Sometimes, like today, I get a notification saying that there has been too much activity from my IP address on ratings, and it won't let me rate. If I'm continuing to rate after I have exceeded my point limit, obviously that's not what I care about. I just wanna rate. But, it blocks me occasionally. So, I try to rate every one, because I do read a lot of them, I'm just not always allowed.
Some are so brief and noninformative I cannot think of anything positive. Or I am uninterested in the product completely after reading, and also I wasn't sure of product prior to clicking and starting to read.
Good point..."if you cannot say something nice......". Well said.
I'm a fast reader and frequently open the 10-15 most recent reviews at a time so after reading a few reviews my IP gets flagged for excessive action so I try to rate all the reviews I read, but sometimes I just can't.