If the aliens are still interested in invading the Earth, cell phones will make it a lot easier than when they tried it using the Beattles' worldwide concert broadcast years ago. Just one transmission of the signal and probably 90% of humans will be brainwashed at the same time
Had a thought a few weeks back about how a zombie apocalpyse would come to a swift end in the age of Facebook, instant messaging/text messages...
"OMG, zombies!"
"Where? Getting my gun/crowbar"
"Down at the McD's, side parking lot"
.
.
.
"Boom! You see teh head 'splode?! Uploading picture"
"Whoa! Txt that to CDC dude!"
"Got vid of it, uploading to Youtube, the cops, and CDC"
"crap, my youtube account got frozen...wait, CDC is now phoning me"
.
.
"OMG downtown is full of zombies!"
"OMG downtown is cordoned off by gunship helicopters and cops!"
"tweet just said there's 10,000 young men walking to the cordon, armed with AR-15's and shotguns, looking to 'purge the infection'!!1!"
Say what you want, but with the speed of Tweets, GPS enabled phones, our smart phones would pass the info faster than the zombies could handle, even the running zombies.
The invasion I'd worry about is the next bird-flu, "Contagion" style!