There is an interesting article on about.com that states the following:
*How many fonts is too many?*
When you can no longer install more fonts you definitely have too many. As a general rule of thumb, you can expect to run into installation problems with 800-1000 or more installed fonts. In practice, you'll probably encounter system slowdowns with fewer fonts. There is no magic number. The maximum number of fonts will vary from system to system due to the way the Windows System Registry works.
There is a Registry Key within Windows (for Win9x and WinME versions) that contains the names of all the TrueType fonts installed and the paths to those fonts. This Registry Key has a size limit. When that limit is reached, you can no longer install more fonts. If all your fonts have very short names you can install more fonts than if they all had very long names.
But "too many" is more than just a limitation of the operating system. Do you really want to scroll through a list of 700 or even 500 fonts from within your software applications? For best performance and ease of use, you'd do well to limit installed fonts to fewer than 500, perhaps as few as 200 if you're using a font manager as described below.
http://desktoppub.about.com/od/fonttechnologies/f/toomanyfontswin.htm
Besides the registry limitation, you have to consider memory limits as well. 600 or more may cause slow performance for a users pc. But I agree that installing a few fonts is a good idea. I have just over 200 fonts on my system and I've had OpenOffice.org, LibreOffice and Microsoft Office installed. I'd be interested to see which fonts are installed with the current LibreOffice installation. Anyone know? I think installing 10 or so fonts with LibO would be a good number.
Ron