Data folder update (<= Neverball r3830)
Of course Tiger is a bit obsolete (2 years) but it's still quite used. Personnaly I use it and I won't upgrade to Leopard or Snow Leopard as I don't need too.
Anyone with a pre-intel mac (including me) will find it impractical to upgrade to 10.5 and higher, as these OS's are designed specifically for these much faster newer machines. In another 2-3 years, most of those users will have migrated I think.
shino, tones, in case you're reading this, given that the three years cited above have passed now, is Mac OS X 10.4 compatibility still an issue for you? It's likely that once LWJGL (the multimedia library I'm using) gains support for Java 7 runtime environments on Mac, getting it to run on Tiger will no longer be possible. From what I've read, Steam requires at least 10.5.8, too.