Description:
The newly released GPSD 2.94-1 package doesn't depend on libusb1, but the gpsd binary in the package links against it.

[chunky@myhost daemon]$ pacman -Qi gpsd
Name : gpsd
Version : 2.94-1
URL : http://gpsd.berlios.de
Licenses : GPL
Groups : None
Provides : None
Depends On : lesstif libxaw python>=2.6 pth
Optional Deps : php: generate a PHP status page for your GPS
php-gd: image support for the PHP status page

<snippage>

[chunky@myhost daemon]$ which gpsd
/usr/sbin/gpsd
[chunky@myhost daemon]$ ldd `which gpsd`
linux-vdso.so.1 => (0x00007fff50dff000)
libgpsd.so.0 => /usr/lib/libgpsd.so.0 (0x00007f46ffc12000)
libgps.so.19 => /usr/lib/libgps.so.19 (0x00007f46ff9fd000)
libpthread.so.0 => /lib/libpthread.so.0 (0x00007f46ff7e1000)
libusb-1.0.so.0 => not found
libc.so.6 => /lib/libc.so.6 (0x00007f46ff48b000)
libm.so.6 => /lib/libm.so.6 (0x00007f46ff209000)
libnsl.so.1 => /lib/libnsl.so.1 (0x00007f46feff1000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f46fecdd000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f46feac7000)
/lib/ld-linux-x86-64.so.2 (0x00007f46ffe50000)
[chunky@myhost daemon]$

I installed the libusb1 package by hand, and now it works fine:
[chunky@myhost ~]$ sudo pacman -S libusb1
resolving dependencies...
looking for inter-conflicts...

Targets (1): libusb1-1.0.6-1

Total Download Size: 0.06 MB
Total Installed Size: 0.21 MB

Proceed with installation? [Y/n]
:: Retrieving packages from extra...
libusb1-1.0.6-1-x86_64 64.7K 107.9K/s 00:00:01 [#####################] 100%
checking package integrity...
(1/1) checking for file conflicts [#####################] 100%
(1/1) installing libusb1 [#####################] 100%
[chunky@myhost ~]$ gpsd -V
gpsd: 2.94 (revision 2010-04-22T10:29:38)