well as i said before, most of the planets that would have life will most likely be more advanced than us. Think of how long ago we developed radio technology and satalites. About 70 years ago. Now think of how long the universe has been here. I don't know, but it's really really really really really long ago.(no offence to creationism.) So, if the alien civilization was to really exist, they would be much, or at least a little more advanced than us. to think that other planets with life on them would just be single cell or micro organisms would be ludicrous too.
The universe is estimated to be approximately 13.7 billion years old. However, considering the millions or even billions of years it would take for ideal circumstances to allow life somewhere (I think it's suspected that the universe would have been far too unstable to support life for the first few billion years of its existence, not to mention the additional years it would take for suns and planets to form), and then the additional millions or billions of years it would take for life to sufficiently evolve to an intellectual point, we're not really so far off. I believe the oldest known life on Earth was found to exist 3.5 billion years ago, so consider that any other place with intelligent life might need a stable and ideal environment for approximately the same amount of time.

if you see my previous posts, you'll see that I posted that "in the universe, there will probably be more than two civilizations with intellegent capabilities" or something like that. :P The example of just TWO specks of dust is, im not trying to make you angry, kind of stupid. If any of you watched any kind of Star Trek before, you will know that there are different species of aliens, such as Vulcans, Klingons, Humans, Romulans, Telerites and much much more.
So, if you add lets say 10 specks of dust, or 100 specks, the odds would increase. There might even be thousands or millions of specks of dust!
Star Trek isn't a good comparison, considering that it's entirely fiction. And of course alien races will encounter each other in sci-fi series frequently, else they would be amazingly dull and uneventful. No one wants to watch a TV show that reflects reality: years of monotonous searching for intelligent life with no results.

And I'm not saying there'd only be two intelligent lifeforms in the entire universe. I'm saying for any two civilizations to come into contact with one another (whether there be 2, 200, or 200,000 in existence), the odds would be less likely than two specks of dust on Earth meeting, given the immense size of the universe.

its not that we don't know, it's that our want to find other civilizations is affecting our judgement. Originally, Dr. Frank Drake(the guy who made the equation) did the equation himself, and got to the answer that there will be 10 civilizations in our whole entire galaxy (which is reeeeally low comapred to how massive our milky way is). But, other scientist and astronomers tried it again, and this time with different numbers. And they got the answer of 1 civilization(which means only us. onoz!!), 5000 civilizations (which is a pretty nice number), and 50 civilizations. I would go with the 50 civilizations. not too big and not too small. the 5000 civilizations would be too much because think of all the galaxies in the universe. Thats just too unrealistic. The one where we are the only one in our galaxy would suck too because the real number is 0.5 or something. Thats a fifty fifty chance in just one galaxy!
No, it's because we don't know. If you study the figure, you'll see we'd need to know the exact number of many things we don't know and couldn't find out with current technology. You are correct that personal opinions do effect the outcomes, but at the moment, any figures are entirely speculative and not precise, so opinion (based on what little studies we have now) is all we can really work with.

And I think the Milky Way is suspected to have somewhere around 200-400 billion stars. Assuming it had 200 billion only, no star was home to more than one advanced civilization, and there were 5000 advanced civilizations, then only 0.000000025% of the galaxy's stars would be home to an advanced civilization (0.0000000125% if 400 billion stars). Those odds aren't really that extreme.