In my opinion I would have to say that some pedals overpower the tone of certain amps, I don't want my amp to lose it's tone and only sound like the pedals in front of it. And certain pedals also rob or overload the signal. Too many pedals steal the tone of the guitar and amp. I'm not sure of all the technical terms to describe what happens when a bunch of pedals are run in series but no doubt they become mushy crap at some point. I guess less is more to my ear, I like a guitar straight into the amp and then add only what you need without killing your tone.
Over the years I have owned many pedals and always seems to get tired of them and sell them all. Right now my new favorite toy is my VOX ToneLab ST, the 12AX7 tube has a very cool sound. I like it.