Words have meaning. Using the wrong words results in causing confusion and making communication more difficult. Please learn and use the following properly.
"Bitcoin Address": A string of letters and numbers typically starting with a 1 or a 3 that is used when creating a transaction to control who will have access to the bitcoins.
"Bitcoin Wallet": Software or a service that allows a user to manage one or more bitcoin addresses along with the associated private keys, and typically provides an interface for creating transactions and identifying the total amount of bitcoins under the wallet's control.
"Bitcoin Account": A service provided whereby you turn complete control of your bitcoins over to the service provider and trust that they will return those bitcoins to you upon your request in the future. (Some service providers will misleadingly call this a "wallet".)
So, I create multiple "wallets" for the same reason that I don't carry my entire net worth of cash in my pocket everywhere that I go. Mainly, security and convenience. I have some cash on deposit in a bank account, I have some cash in a safe, I have some cash in my pocket, I have some cash in assets, etc. Similarly, I have some bitcoins in a "paper wallet", some bitcoins in Armory, some bitcoins in Coinbase, and some bitcoins in Blockchain.info.
I create a new bitcoins ADDRESS for increased privacy and slightly improved security. If I only use one bitcoin address, and I give you that address so that you can send me a small amount of bitcoins, then you can look on the blockchain and see with absolute certainty exactly how many bitcoins I've received in the past, and on what date and time I received them. If others that sent bitcoins to or received bitcoins from have made their bitcoin addresses public, then you can see when and who I've been sending my bitcoins to, and receiving them from and how many I sent or received in each transaction. You'll also be able to continue to monitor all of this information about my personal finances in the future.
Hey Danny, great add here. I also want to thank you for finding a solution to your personal frustration with signature ad campaign posters. Everyone, see DannyHamilton's signature, he's made a list of those of us that have an signature ad and ignored us so he doesn't see our posts. That's a great way to deal with it! Another great way to deal with it (if you're sick of seeing ads) is to elect to not see signatures of posts, which you can select in your account profile settings (look and layout).
We CAN coexist and remain productive to the community.