Created an attachment (id=6815)
Annotated debug log
r54059. Virtualbox 4.1.2. Ubuntu 11.10.
Using the installer from steampowered.com (1.5MB), Steam seems to install properly. However, when it first launches, it tries to download an update (which it can't for some reason). The update installs 95MB of additional files.
After installing in wine on the host PC and copying the Steam folder manually, it still doesn't launch. If you read the attached file, there problems with the clientblob file before and after copying the files, although the error changes.