php-openid/2.1.1 (php/hphp) curl/7.19.4

Something new from Facebook comes...

[Pfui]

(Wasn't sure how to title this minus the version numbers, so there they are.)

The following Facebook-registered servers hit the same site one second apart:

out.247.01.snc1.facebook.com
php-openid/2.1.1 (php/hphp) curl/7.19.4

robots.txt? NO

69.63.182.122
php-openid/2.1.1 (php/hphp) curl/7.19.4

robots.txt? NO

That combo UA is new to me generally, and definitely related to facebook hits. (PHP OpenID? cURL? From Facebook?!) Vis-a-vis that site, it may be new most places because Googling facebook plus the full UA yields a whopping 2 hits.

[Pfui]

Different site than preceding post's hits; four hits x2 days. And all --

php-openid/2.1.1 (php/hphp) curl/7.19.4
robots.txt? NO

-- with no facebook.com or tfbnw.net hits/referers x30 days, ditto none of the usual UAs (Facebook share follower; facebookexternalhit); only .html, no graphics, .css, .js, etc.:

66.220.146.247
17:33:24

69.63.181.251
17:50:33

69.63.181.250
08:22:56
17:50:22

Why so stealthy? Spidering?