Linux does not put arbitrary limits on the number of hard disks.
With IDE, ATAPI, ATA or SATA drives, you are limited to two disks per channel (master and slave), and usually two channels per controller. But you can still install extra controllers as expansion cards.
With SCSI drives, you can daisy-chain more devices on a single controller (Googling for this, I think 6 might be the typical limit, but you may be able to get more than that on some controllers). Again, you can get additional controllers.
With USB, you can attach as many devices as you like, up to a few hundred per controller given enough powered hubs. Again, you can buy more controllers if you like, but note that the bandwidth is split between all the disks on one controller (and USB hard disks don't tend to have a good size*speed/price ratio).
Inside the kernel, the settings for each device are stored as a vector of device nodes (If I remember rightly), so you even can have as many devices as you like running from the same driver inside the kernel.
In practice, the limits are likely to be the cooling power of your computer (I'd recommend hard-disk coolers if you're running many drives, especially in a smaller box), and the limits of your computer's power supply.
To put more than a few dozen drives in a single box, you may also need to create more nodes in the /dev/ filesystem before Fedora will see them. Alternatively, you could use a hardware RAID controller to combine them into a single device.
You can also have as many software RAID partitions as you like.
Hope that helps,
— Robert J. Lee