It appears that man has a what is referred to as a war gene. Its a self-destruct mechanism built in that assures we will never survive past a certain point of evolution. This being so, do you think the reason we are not in contact with alien civilizations is do to the possibility that they reach our level of technology and kill themselves off, with the new energies they learn about? Example Earth present time.
The notion that we are naturally war-like is popular but has a few holes, actually. From archeological data, it may be entirely possible that we never waged war before we started having private property.
And if many civilizations on earth crumbled at some point, it was almost never to the point of destruction. Rome wasn't erased from the map in the 5th century, it continued to exist but stopped being the powerhouse it was before.
Today, we see a lot of signs showing the human race realizes some of its limitations and is taking steps to correct its course. Maybe tens of millions of people will die before we do it enough, maybe even a few billions. But that doesn't mean human extinction.
Two factors make this a popular theory. Firstly, intelligent species are almost always going to develop (via evolution) from predators. There is a simple reason for this; intelligence costs a massive amount of energy to maintain and there has to be an environmental advantage for it to happen. Predators can use it to catch their prey via coordinated strategy (rudimentary language skills and ability to remember how prey react in certain circumstances). Prey just have to be able to run.
Secondly, the environment is delicate. Ecosystems are the ultimate implementation of complex interrelated supply and demand curves, and as intelligent species learn more about it, they learn more and more creative ways to disrupt it. The trouble is, all it takes is a single intelligent fool in your population to do something that can cause wholesale (possibly complete) destruction of your civilisation, and potentially the species itself.
Stopping that from happening entails bringing the entire population along on a journey of social development that can keep pace with technical development. We (as a species) are hardly exemplars of that ability ourselves. And yet, even I have to concede that we're still alive. For now, at least.
We can't know for sure, but I suspect that the number of intelligent species out there that end up destroying themselves could be high, if a species get that far. Still, I think the answer is actually more pedestrian.
Most species simply won't get the chance to live that long.
The universe, when you get right down to it, is a very hostile place. We're just lucky that we're on a planet ideal for hosting life, in a relatively remote area of the galaxy (meaning that we're not close to a lot of supernovas or black holes), with a Jupiter sized planet out there eating up most of the stray asteroids, and our sun is particularly small, meaning long gestation period for life on Earth. Most intelligent species won't have those advantages and are just as likely to be wiped out by a hostile configuration of supernovas, expanding suns, stray asteroids etc. Not to mention that the ideal conditions for the development of life (let alone intelligent life) is going go occur at completely different universal epochs all over the galaxy (not to mention other ones) due to the fact that stars form at different times and live (and age) at different rates.
Add to that the tyranny of distance and relativity, and any civilisations out there sending us messages will probably evolve into new species by the time we receive them, assuming they're alive at all (given the above). This assumes that their technology evolved down the same path as us and they're not sitting around scratching their 'heads', wondering why no-one's responding to their gravitational radio waves, 'after all, they're so easy to produce that every new sentient species would figure that out first, right?'
To summarise, this theory does hold some weight, but given the depth of things that can 'go wrong' with intelligent life, I'm not convinced this would be the primary cause for our isolation.