Funny, I've been using breadboards for many years and have never had one cause a problem. Lots of stuff built on them didn't work at first (or ever), but it was never the breadboard's fault. I have two from RadioShack, bought around 1990, a couple of 3M, and a hand full of random types acquired over the years.
They're made to use with small wire and leads only. If you jam something way too big in them, or try to use those tact switches and pots with wide, flat leads, it's possible to spread the clips to a point where small leads or wire will no longer make good contact.
They're not intended for high speed circuits. I have no idea what the limit is for any of my boards, but I've made 4+ MHz oscillator's that worked fine. This is because there will always be a small amount of capacitance between rows on the board which will affect any circuit built on them. It may be enough to cause problems. I think Dave measured his breadboard in a video and found around 20-25 pF.