Google Rankings

[anaxcrosswords]

I've asked my webhost to block bots/crawlers from my clue-writing forum as they were eating data (the forum has been offline for about a week because we ran out of bandwidth). Obviously, a result of blocking the bots will be the forum gradually falling down rankings, but is it important?
It's a small forum, and new members almost entirely come from online articles, blogs and website links. I imagine very, very few people search for it.
Are there any other adverse effects of a site falling down the Google rankings?