I don't think Dreamhost publishes a hard limit, but I can say that they seem to have allocated 150 million inodes for the filesystem that my files are on and of that about 50 million are in use. This doesn't say anything about how many inodes any individual account is allowed to use.
BTW, I think there are still some performance implications to having too many files in a directory.
In case you want to understand more about the relationship between inodes and files, read what WikiPedia has to say about inodes.
Use the [color=#CC0000]3DOM50[/color] promo code for 3 extra lifetime domains and $50 off
More Dreamhost coupons here!