The "breadboards" that I've had for the last 30 years, though I don't use them more than once every three or four years, have a solid metal plate beneath the socket array. Even grounding that, though it's only aluminum, is really not adequate to provide a ground plane, probably because it's too far from the circuitry itself.

It's true, you can build a really terrible implementation in just an hour or two, but it won't be stabile, and it won't be the same tomorrow as it was today.

If you want something that behaves consistently, and/or something that lasts, you need to solder or wire-wrap it.

Solderless breadboards might work OK for experiments that only have to last long enough to poke around on them with a 'scope, but it's far too easy to disrupt the circuitry with "normal" handling. Unless you cut each wire to the appropriate (minimal) length, and keep it close to the board, the circuit will be subject to external influences such as noise, or even pickup from your hands. These "breadboards" are OK for audio and sub-audio (DC) circuit experiments, but, as I said before, while they may be OK today, all bets are off for how they'll do tomorrow. I think they're a pitiful waste of money and, even more so, of time. For what I paid for my "solderless breadboards," I could have purchased a significant supply of wire and sockets for use with wire-wrap. That's what I eventually had to do anyway in order to create stabile circuits.

RE