How NASA might build its very first warp drive
io9.com
io9.com
It would seem either intelligent life is sparse enough in the universe at this time that we have not been found, or we are being intentionally ignored.
The previous explanation - that the universe is too spread out and interstellar travel is impractical - would no longer apply
The amount of time for which life exists on a planet, from genesis to extinction, is extremely small on a universal scale. Intelligent life may not persist on a planet long enough to develop a means for intergalactic expansion. Even if they succeed in this endeavor, it is likely that they will be wiped out eventually by some means.
Basically, the likelihood of multiple intelligent species existing simultaneously and within adequate proximity for one to make contact with the other is extremely small. It's hard to overstate how lucky we would have to be.
Travelling to Alpha Centauri in 2 weeks means travelling about 4 years 3 months into the past. If that holds true then leaving today, spending 6 months "at warp", you could look back on Earth in the early 1960s. After a 2 year journey Earth could be seen in the early 1800s. Travel for 25 years, and see Earth in 500BC.
I think the point of my comment still stands regardless of this revision. If you could choose exactly the position in time at which you'll land, then we have a different story (though this would likely require unreasonable travel speeds).