I do think it is rubbish and that it's irrational to believe in this stuff, too, just like religion.
I have not read the whole thread, but somebody said above that astrology is harmless. My parents come from a culture (Hindu), where astrology is taken extremely seriously. Arranged marriages can be determined by astrological compatibility. It's frightening.
My own crazy mother used my star sign as a rod to beat me with growing up, consistently using astrology as a weapon (eg, if I asked her to stop shouting) and labelling me with the "qualities" of my sign, which aren't particularly flattering. It's damning to be told you are critical, fussy, boring, graceless etc etc day in day out for no good reason other than she could and knew it would shut me up.
I started to believe it and it took me a long time to realise I was a lot of things and not simply a set of generic attributes that magically flew into me the minute I was born. She did this to my siblings too. Certainly, 2 of us will not even talk about our own children's star signs, we don't want them labelled like we were.
That's a rather rambling way of me saying that any belief, taken to extremes, can be dangerous, even something as seemingly innocuous as astrology. And imagine you are in a culture where you are not allowed by your family to marry the person you love because they don't think you are compatible.