SETI research has been around for a long time. A lot longer than most imagine. See http://www.msnbc.msn.com/id/28916124/
I think the modern approach is missing an import consideration - Probes. Yes Probes. We have been only to send objects into deep space for last few decades and Already we have a collection - the voyagers etc. Some dead but nevertheless there.
So imagine a half dozen E.T. civilizations older than us sending out probes of varying complexity and sizes. These must number in the hundreds of thousands if the evolution of intelligence is more than a fluke.
The sizes of probes could present a problem however if they are active mostly likely are sending out signals. These signals could be detected mitigating against the size problem.
We should guessestimate the rage of power and frequencies that probes could have and thoroughly investigate small (targeted) patches of sky. We should target nebulas and places that are or were "interesting". while avoiding areas that life could evolve and then caputure or destroy any alien probes.