Use of bitcoin client would be easier for him if all data expensive operations are done by third party client (for example my client) and his client would be able to verify found transactions and and them to his wallet.
that's what SPV clients, like electrum and multibit, does. they don't need you to download 70GB~ of data.
If the BTC electrum servers get taken down or offline or whatever then those who use it run the risk of losing their coins unless they have their private keys saved for their coins.