Should blank user agents be blocked or not?

[aristotle]

I'm currently trying to improve the .htaccess files for my websites, and am wondering if I should remove some code that I added some time ago for blocking blank user agents. I don't remember exactly where I got it, but the code is as follows:

# BLOCK BLANK USER AGENTS
RewriteCond %{HTTP_USER_AGENT} ^-?$
RewriteRule ^ - [F]

But in an article about blocking user agents at [perishablepress.com...] , I found the following statement:

To accommodate Facebook (and others) traffic, the empty/blank user-agent is no longer blocked, which is unfortunate because of its effectiveness at blocking bad requests.

So the question is, should I remove this code from my .htaccess files or not?

[wilderness]

Each webmaster must determine what is beneficial or detrimental to their own site (s).

I deny Blank UA's as do most others (it's a simple procedure to add exceptions to the same rule).

Personally, I deny the FB bots as well as FB Refers, however that's my preference.

[dstiles]

I block blank UAs. I only see FB hits with a UA. Possibly they are blocked for using an already-blocked IP range such as amazon.

[keyplyr]

I block blank UAs, but allow several ranges through that are beneficial (FB and a few others) YMMV.

RewriteCond %{HTTP_USER_AGENT} ^-?$
RewriteCond %{REMOTE_ADDR} !^xxx\.xxx\.xxx\.xxx
RewriteCond %{REMOTE_ADDR} !^xxx\.xxx\.xxx\.xxx
RewriteCond %{REMOTE_ADDR} !^xxx\.xxx\.xxx\.xxx
RewriteRule !^robots\.txt$ - [F

Note: replace the "xxx" with actual ranges you wish to allow to use a blank referrer. This is site specific and different sites will see different agents as beneficial or not.

Also, I allow all agents access to robots.txt, even ones I block for various other reasons.

[aristotle]

keyplyr wrote:
I block blank UAs, but allow several ranges through that are beneficial (FB and a few others)

This seems like a good approach to me. Would it be too much to ask (or at least give a hint) which ranges should be allowed and what would be the best way to do it?

Edit: keyplyr I apologize. For some unknown reason, I initially only saw the first line of your post and didn't see the rest of it until now.