Lots of brides have gone through this- and it wasn't even the economy's fault. Yes it totally sucks how everything is on the rise and I totally feel for you upcoming brides. But I think it's also giving your guests more of an excuse to play with. If you search this forum, you will find that even in 2006 the brides were struggling with guests not coming for various reasons- number 1 excuse was the cost associated with a DW.
Granted those that have lost jobs due to the recession can't exactly be blamed for not committing. I think the best attitude to have when planning a DW is being thankful for those that can make it, and not even think about those that can't. If you dwell on the have nots, you will spend most of your time being unhappy.
As others have said, those that want to go will still make it happen. Even with things getting shitty, we are still planning trips for the next year because we still want to vacation. We will just have to cut a few corners in our budget to make it work.