Actually this issue must be taken into consideration. There are different ways around it, like i.e. strong "smart pullups" that put a lot of current (maybe overvoltage? I didn't really read the paper very thoroughly) into the line while the line is pulled high (i.e. for period between the zeros) so the capacitors recharge faster. There are many ways, i.e. the microlan switch - a 1-wire device that works as 1-wire line master, with external power, so if you attach a lot of devices, you split the line into a network of smaller segments, each of them powered by its own master, all masters connected with one 1-wire bus.
Get the latest issue of Dallas Engineering Journal (available online on Dallas site), there's that paper about the 1-wire power problem solutions.