[progolferyo]

A quick and dirty solution could be to add something to the page using javascript after the page has loaded and only let the link work if that variable exists (and check the value of the key with the server, if you wanted to be more cautious). Not a complete solution, but a first step and invisible to the user (and a pain in the ass to a robot)

[waitwhat]

A robot scraping yelp's deep data is going to be site-specific, and having to scrape another javascript variable is not much more than a slight speed-bump.

[jrockway]

Scraping with a normal web browser is utterly trivial. Anything a computer can do, a computer can do. Hence CAPTCHAs.

[soult]

Yelp does not just want to make scraping impossible, they seem to also be interested in making it harder for humans to view filtered reviews.