Geez, talk about misinformation!!
The $150 price includes the broadband adapter. It seems the Japanese market is not getting a BBA/modem hybrid, it is just a BB adapter judging from the pictures (since they only show an ethernet port). The hybrid BBA/modem was shown at E3 so it\'s probably only for the North American market (maybe UK) where dial-up connection are much more entrenched.
Therefore, the harddrive itself is really only $100 if you factor in the $49.99 price the adapter was announced at.
You DO NOT need the HDD for most of the online games. Tony Hawk, Twisted Metal, and most of the ones announced at E3 do not require the harddrive. Therefore the success of the HDD really has nothing to do with general online gaming on the PS2.
However, MMORPG games such as FFXI (if it turns out to be a MMORPG and not level-based like Phantasy Star) will probably require the harddrive just because of dynamic online updating and stuff like that.
There\'s also a list of games circulating that will support the harddrive. Most of them are games that will only ever be released in Japan at the moment, and most simply use it to decrease load times -- like FFX -- but there are a few train simulation games on the list that will allow new trains and stuff to be downloaded for use in the game.
To summarize:
The $150 bundle includes the ethernet adapter.
You do not need to the HDD to play most online games.
In the US the BBA/modem hybrid and the HDD will be available separately. Whether there will be a bundle deal in the US has not been announced yet as far as I know.
There are games in the pipe now that will support the HDD upon their release, though none require it at this time. This may change with MMORPG online games though, since they may require the HDD.
Some developers have noted that it is extremely simple to add support for the HDD to act as a cache and therefore reduce or eliminate load times. The up point for the developers here is that they can market the game as supporting the HDD (though not requiring it) with very little effor on their part.