This would be horrible! Macromedia has done a fantastic job of advancing their products to be very standards compliant and cross-platform. The Register points out:
An acquisition, though, would be seen as a hostile move deliberately designed to thwart J2EE uptake. Flash is a powerful and rich development environment, which - through Macromedia's changes this year - took a step closer to J2EE.Flash, Coldfusion (by deploying on J2EE app servers) and Dreamweaver are all cross-platform, both on the client and the server side.
Again from The Register:
A Microsoft acquisition of Macromedia would inevitably see Flash, and Macromedia's other cross-platform tools, tailored purely for Windows and .NET.Aaaaaahhhh!!! (Sounds of Boris running screaming around and around, tearing at his hair). I really, really, REALLY hope this doesn't happen. Perhaps I should call Lloyd and get him to see if IBM will buy Macromedia instead...