A WebmasterWorld thread asks, "Are There Negative Consequences to Pausing a Campaign or Adgroup?"
There is a lot of speculation in the thread, but I believe the bottom line is that there is no direct consequence for pausing a campaign or adgroup in Google AdWords.
Deleting a campaign or AdGroup can and will cause issues. Editing a campaign or AdGroup can also cause direct issues. But pausing them should not.
AdWordsAdvisor basically confirms that, but we are waiting on confirmation on that.
What may happen is that your competitors gain better history for their ads (but your history should remain the same). It also may hurt you to not remain active, because this is a dynamic bidding and ranking environment, if things change and your not around to watch these changes, then you can be hurt from the lost experience and time.
Forum discussion at WebmasterWorld.
Update: AdWordsAdvisor2 confirms that pausing ads have no affect on your quality score at a WebmasterWorld thread.
Pausing campaigns or Ad Groups has no effect on your Quality Score. Feel free to pause or use Ad Scheduling as necessary.