Of course not, if you don't want to run the node client you can use some other 3rd party APIs such as http://www.myetherapi.com/, https://infura.io/ (which is the one metamask is using already), https://etherscan.io/apis

Can even create the transaction on your own and then use tools that will enable you to push your transaction on the ethereum blockchain, which mostly these APIs listed above have the ability to do.