Yep, this is the kind of thing that makes me question my choice to go Delta... then again American is starting to do the same thing.
Delta without any warning, which is hardly surprising for Delta, raised the lowest possible award rates to take business class flights to Europe. Originally that rate was 62,500 miles, but without warning Delta raised that price to 70,000 miles yesterday. While I don't think this is an insane change, it is not a good one. I find that raising award prices in a market that no longer highly favors the airlines is a costly move for any company to undertake.
By taking a measure like this, you are hurting the one customer that will stick with you even when revenues are down. Award prices really shouldn't vary as quickly as they do. This is just an obvious attempt to limit what people can do with mile... but those of us who really want to make miles/points work, will find a way.
So my advice is to adjust as always, continue earning miles and keep on flying.
This change is not immediate, but goes into effect for travel after January 1st. So you will be able to find the previous ticket prices of 62,500 miles prior to that date. If you want to grab a cheaper miles seat, go check out a flight that gets you to Europe before January 1st. After that, you're going to see the raised award prices. This is why Delta no longer publishes award costs, so they can change on the fly... and they will continue to do this. American is right on their heels and is starting to do this as well.