I was going to say that maybe a DS can download a keyboard (it already has one in PictoChat so they could just adapt that), so Nintendo could encourage people to buy a DS Lite. After all, unless you already have an extra USB keyboard, and unless the Wii can actually support USB keyboards, a special Wii one would probably already cost half as much as a DS Lite. That is, if you don't find the DS Lite too small.
If you only visit sites where you don't need to type (webcomics, news sites) you could probably bookmark all your favorite pages and then you shouldn't usually need a keyboard again after that (except maybe to add more sites).