I look after an affiliate site that is doing quite well in the search rankings. We've been doing a review of our practices and one thing that has cropped up is our robots.txt.

In it, we disallow Google from crawling external links. This used to be best practice in the affiliate industry a couple of years ago, but I wanted to know if this is still the case, and what the implications are if we were to:

a/ leave it as is?

b/ allow crawling?

Thanks in advance.