The bitcoin currency currently offers no major advantage over USD. Everything you can do with BTC, you could also do (well almost) with USD.
Creating services which are available only using BTC may give this extra push to the bitcoin currency so it doesn't lose its value totally as seen in the last days rate.

Bitcoin Message Service which was announced https://bitcointalk.org/index.php?topic=47283.0 earlier this month and mentioned https://bitcointalk.org/index.php?topic=48989.0 among The Bitcoin killer app list, aims to this direction, giving an option to write messages into the block-chain which means order of 10^6 scattered copies around the globe safely kept by individuals, impossible to delete messages and possibly anonymous. Such a service would not have been possible before the bitcoin times, and it requires the use of BTC.

Using such a service directly contributes new users to the bitcoin community.
Are there more such services? Do you know any plans plans for such services?