Colossus telescope, trying to outsmart aliens?
The real reasoning has nothing to do with some civilization "deliberately" hiding its radio emissions. Rather, the problem is that we can not expect some other civilization to do something we would not do ourselves.

It makes no sense whatsoever to radiate large amounts of energy into space when there exist other, more economical alternatives. Radio transmitters circa 1911 required whole dedicated dynamo machines to run at abysmally low efficiency - these days we are using tiny battery powered devices with directed radio beam steering and adaptive power minimization as to not transmit a single joule more than absolutely necessary to get the data through to intended destination.

Another problem arises from the fact that most of the "radio SETI" effort to date was concentrated around the "cosmic waterhole" (the frequency of interstellar hydrogen emission). This is a reserved frequency here on Earth, so nobody broadcasts on it. Common sense suggests that aliens would probably do the same - after all, we expect them to have developed radio astronomy as well. Unfortunately, listening on any other frequency will probably pick up locally generated broadcasts first and completely mask the weak alien signal.

Given the above, what choices are we left with? One would be to construct a large radio telescope somewhere Earth radio emissions can not reach - the far side of the moon or even a trans-solar location on the Earth orbit come to mind. Unfortunately, such project, while doable, is hugely expensive.

The other approach is to develop "distributed" telescopes which can be built gradually on low budget and to develop techniques to cancel the local noise. For low frequency radio telescopy such project is already ongoing:

http://en.wikipedia.org/wiki/LOFAR

For infrared, we've got this "Collosus" proposal, but place our hopes on JWST (http://www.jwst.nasa.gov/).

And we don't expect to see much in visible light for all the obvious reasons.