As has been said many times blocking spiders/bots is a personal thing, you need to understand who and which countries you are aiming your site and content at, do you have enoughj resources to allow your content to be scraped by archivers...etc, do you have enough bandwidth to allow bots who add no value or do not cater for your target audience to index your content?
Just be very honest with yourself on what your intentions are with regards to your target audience and user experience