Importance:
Medium
GG reponds to a question about how long a disallow command in a robots.txt file will take to affect Google results.
GoogleGuy Says: [
Link to quote]
I think it should be much sooner than a month. If it were an office pool, I'd bet on less than 10-14 days. Let us know when you start to see pages leaving (it will probably be a gradual process as we try to fetch each page and find the robots.txt).