The good news is that the merger of Blackwell's digital content with that of Wiley's has not affected the DOIs, which is exactly as you'd expect, and is a nice demonstration of the power of identifiers that use indirection (although there was a time when Wiley was offline).
For example, the article identified by doi:10.1111/j.1095-8312.2003.00274.x had the URL
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8312.2003.00274.x and now has the URL http://www3.interscience.wiley.com/journal/118833573/abstract. The DOI, of course, hasn't changed, so anybody linking to the paper via the DOI (for example, in a blog) won't be affected.
Naturally, not everything is rosy. The Canadian Journal of Zoology has managed to break just about all their DOIs. Surely the must come a time when CrossRef starts automatically checking DOIs and alerting publishers when they are broken?