Those that put road blocks in the way such as using CAPTCHA or other techniques are classified as hostile services. Another requirement is that it should also operate properly in Android's Orfox, the Android's kind of equivalent to Tor Browser.
If it works in laptop/desktop Tor Browser and not in Orfox, it is still classified as hostile. Any service that requires log in etc. even though not presenting any hostility road blocks is placed in the "Useless" category. Too much trouble.
Tor Browser users should black list those hostile services as they do not possess any uniqueness as the review below shows there are friendly alternatives. In that way the Tor community can deny them of visits and advertising dollars, much like AdBlock Plus.
Tor users can refer to this Tor Project sites for more comprehensive list of Tor hostile sites.
Only 5 out of 10 are Tor friendly. Naturally Google is one of the hostile one.
Tor Friendly siteBitly
In Orfox, one needs to add cloudfront.net and Googleapis.com to NoScript's whitelist.
There are times that this site demands CAPTCHA validation and need more experiment to determine its friendliness.
One needs to add this to the whitelist in the NoScript in Orfox.
Given this is in beta, it loads slowly but still works in a no-nonsense manner. Hope it will not be hostile to Tor as it matures.