Please note that limiting connection bandwidth on a Bitcoin node (either bitcoind or bitcoin-qt), *especially* while listening to connections (that is, without setting listen=0 in the configuration file or -listen=0 on the command line), is in fact, harmful to the Bitcoin network. If you accept incoming connections, other nodes will connect to you. When you're relaying data, whether this is transaction or block data, the data will reach your peers slowly. The reason that this is more of a problem when listening to connections is that if you listen for incoming connections, a peer that is in the process of the initial sync with the network (either a new node, or one that has been shut down for a while) may connect to you and request blockchain data from your node. At the moment, the software selects one node to sync from, and requests data only from that node. If a peer is attempting to sync from your node and you have throttled the connection, that peer will be damaged.
