Good luck doing a job or phd interview on google talk. My understanding is that skype has patents on a myriad of things related to live audio/video. Plus it works really really well and does screen sharing too (which means you can do presentations online). It's not just the network effect here. It's actually a better-than-the-rest product (and i sure hope MS won't make it a mess). Plus, its not less free than gtalk .