Buying used or sight unseen speakers a bad idea?

My advice on buying used speakers: buy local or make sure that the seller has the original boxes and foam packing. Only buy from someone with good A'gon feedback who either posts pics or emails you some. Good communication is a must. If a seller really wants to make a good honest deal, you should not be waiting around for a response to your email.
I bought my last pair open box from audio advisor, I get a full manufacturer warranty and they were half price. I'm thrilled with them. There was some hidden damage, but audio advisor took very good care of me. My experiences buying from A'gonr's has also gone very well. The used amp I bought started blowing rail fuses, but worked flawlessly for 6 months before that happened.
I cannot stress enough the importance of having the original packaging with the original foam inserts for heavier equipment. The box my pre-amp was in got practically crushed by UPS. Not really the sellers fault, he told me he didn't have the original packaging but would double box. He did, also wrapped with bubble wrap and filled with peanuts, which probably saved the unit; the box looked like it'd been run over with a forklift. the foam inserts would have better protected the pre, which was luckily undamaged.

Another quick note: try to buy brands that are sold in local dealerships near you. That way you have access to repair techs that are in your area. You are also able to audition their products, then go out and find them used. When my Rotel amp starting blowing rail fuses, I took it to ListenUp here in Denver. They are a Rotel dealer, and the front desk guy was a little reluctant, but they have repair facilities onsite, and took good care of me. My Halo Pre can be supported by Gold Sound, a brick and mortar shop that's been in business for 20 years. Otherwise if something breaks, you have to ship it off to some out-of-town joint.
I do not recommend buying speakers unless you've listened to them first...

@ Bifwynne, you sound just like a dealer. Just because I don't buy that particular set of speakers I'm auditioning, doesn't mean I won't come back at a later date and buy something else. I've spent thousands of dollars at ListenUp, and I did not buy every single thing I listened to. I also did not buy something every single time I walked in the door; in fact several times I enter dealerships without the intent of buying anything. Its called browsing.
I've spent hundreds of dollars at Gold Sound, and I didn't buy everything I listened to. I go into these dealerships a lot to listen to new gear and check things out. I don't make a purchase every time, sometimes I buy new, sometimes I buy old. Whether or not I am going to make a purchase should not affect how I'm treated in the store.