We have traffic coming from both Google and Yahoo, but can anyone tell me, which one of the traffic is more useful? I wanted to know this for a very long time .
That's not true. I"m receiving a lot of traffic from Yahoo, Bing and local search engines. Some busy traffic exchanges are also good source of traffic.
...and how about Twitter and Facebook??? Do you recive traffic from this sources?
As per my views mostly people use Google rather than yahoo, MSN and bing. However, traffic is always beneficial for your website, it doesn't matter that from which source you are receiving traffic. A user get more happy when he found useful information under one click.