It is very difficult for any one to compete with the Google in traffic genereation, as it is the larget used service on the internet, therefore i don't think it will be very difficult for anybody to compete with it, even for twitter and facebook.
Twitter is growing and fast and by looking at its popularity i can say that in guture it will be a very good competition for the google in traffic comparison.
I purchased 5000 twitter followers from www.socialkik.com and they delivered them sooner than promised, that made a huge positive impact on my online business ! I started receiving more customers and better conversion rate because of the big number of followers which enhanced my reputation ! I highly recommend them www.socialkik.com
Twitter visitors leave more quickly. Google visitors spend 90 seconds longer on our site than Twitter visitors. Bing visitors, even longer. Traffic from Google is much higher quality than traffic from twitter. Twitter as they are very big source of traffic.
I think twitter traffic is better than the Google traffic as twitter is new and it is having better followers than google. Also twitter has good features to attract visitors, as you can add site url to the profile. And maintain your site with good content.
I don't think that any body can compete with google, though twitter is a very good netwroking siet and is very much capable of producing 1000s of hits but i don't see it a threat when it comes standing against a giant like google,.Google is the most popular online site and generates 1000s of list.