How sites like Orkut gain Money??

Have you ever wondered how social web sites are providing you all free-services for you to sit back and chat with your friends? If you want to call next street guy through a mobile; it charges you right for telecommunication charge and you recharge or top up to proceed to use their service?? But how come so good or so free of cost these social web sites are providing you free service.
The answer is Google.
To know better, first know that Google bought Orkut just to get hands on all Indians and Brazil. So, they waited for some time to see some statistics. Once they found that they have achieved quite a good number of profiles or users, they started putting their ads in the site.
I hope you would have noticed some ads in your Home Page based on details you have given or based on communities you joined. If you have not checked; please do check you may find one.
So, Google is clever that it did not show ads while starting orkut but since now many users have account and friends shared, the users can’t delete their accounts anyhow. Google gets the money from the clients for showing their ads in orkut. Clear??
How any site can earn money through Online?
The earnings for any site through online are of 3 methods.
1. Ads- This is the revenue for the Great Google. How ever, other site like Yahoo and others also get their own ads from their clients.
2. Membership coupled cost- these sites will offer some features for free and rest of them you need to buy. How clever, once we are half way through site and we liked it, we need to improve our membership to use better.
3. Selling Service- You might come across with downloading E-Books, Software, or any such stuffs from internet.
Concept of E-Commerce:
E-Commerce is an electronic way to activate commercial things such as Order, Selling, and Purchasing at Online.
You might see in internet that many sites say for pay-pal and credit numbers through online. Many products are sold online like cosmetics, electronic goods, computer parts, commercial stuffs etc. Also you may find Hosting services use E-Commerce.
Advantages of e-commerce: It helps the customers by cost and price reduction and helps the suppliers by eliminating intermediaries in selling.