Well it depends. Data storage is pretty portable. However once you start coding for the cloud, well, as ever, if you're writing ASP.NET (Mono aside) then you're going to have to use IIS. PHP gives you options of linux/bsd/windows. Rails, well, rails doesn't
work that well on Microsoft, so now you're locked into Linux, and that's only a little better because you might have more linux cloud suppliers.
Ruby on Rails is available for Windows, it is MIT licensed, and there is nothing stopping people from running it on Windows under cygwin if they do not like the Windows version. If people do not like the Windows version, there is nothing stopping them from
modifying the source code to produce something that they do like.