I stand corrected, you do not need Leopard before Snow Leopard.
See this from the Apple Store web site:
To upgrade your Mac to OS X Lion, you must be running OS X Snow Leopard. If you have OS X v10.5 or earlier, purchase Snow Leopard now and install it on your Mac. Then buy OS X Lion as a digital download from the Mac App Store
Also, make sure your Mac specs are compatible. There is a rumour that Apple will be selling Lion on USB. I'm not sure what the requirements will be for this.
Lion/101.7 System requirements
• x86-64 processor (Macs with an Intel Core 2 Duo, Intel Core i3, Intel Core i5, Intel Core i7, or Xeon processor.)
• At least 2GB of memory, (I say 4GB)
• Latest version of Mac OS X Snow Leopard (10.6.8), with the Mac App Store installed
• At least 4GB of disk space for downloading, (I say 40GB at least)
Like Snow Leopard, Lion does not support PowerPC-based Macs (e.g., Power Macs, PowerBooks, iBooks, iMacs (G3-G5), eMacs).
Lion also does not support 32-bit Intel Core Duo or Core Solo based Macs. Rosetta is no longer available in Lion, which means Lion no longer supports PowerPC applications.