This might be a bug tickled by the latest version of rspec, because I've been using rspec and backgroundrb for ages without any problems.
What I'm finding is if I run 'rake spec' from a rails project with the backgroundrb plugin and a backgroundrb.yml file which specifies ":environment: development", line 23 of bdrb_config.rb sets RAILS_ENV to 'development'. This means that rake spec clobbers the development database.
actually it seems to be from line 28:
environment = ENV["RAILS_ENV"] || config[:backgroundrb][:environment] || "development"
if the libs are loaded by the normal rails loading mechanism from rake spec, it sets env to development.