Some say Linux's .rpm and .deb installation packages uninstall cleanly, so there is no need for any registry cleaners like CCleaner. Here are a few counterexamples to the myth:
Years ago you installed OpenOffice.org version 1, and since you've upgraded to version 3. Now you wonder why Firefox still associates .doc files with OpenOffice.org version 1, which you long ago deleted.
OpenOffice.org didn't support .rpm or .deb installations until version 2. Version 1 copied files (including file associations and menu entries) to the user's home directory.
For users without root privileges (or just for convenience), RealPlayer11GOLD.bin installs itself to the user's home directory. Unless you use an arcane command to uninstall RealPlayer, dozens of files remain in ~/.local. I counted three menu entry .desktop files, 20 file association .desktop files, 206 PNG icons, and some translations.
Install Beagle (an indexing search tool), and it may add itself to ~/.config/autostart/, a directory for automatically starting applications with the window manager (GNOME or KDE). Then, uninstall Beagle using the standard .rpm or .deb removal method. However, the package removal method doesn't touch ~/.config/autostart/.
Install a Windows application on Linux though Wine, and Wine will integrate the Windows applications with your Linux applications. Convenient! Now, as is common with Wine, delete ~/.wine/, but the broken menu entries remain.
Unfortunately GNOME and Wine doesn't handle this situation gracefully. If you click on any one of these shortcuts, there is no error message whatsoever. Technical, the shortcut points to Wine, which is still installed, so GNOME is not aware of an error. Wine prints an error message to stderr, but that's never shown on the screen. Also, GNOME doesn't support menu editing through the intuitive right-click command.
These are just a few examples of why Linux needs a smart cleaner. It's true that there is no central "Linux registry" like Windows has, but Linux certainly does have multiple systems for registering menu entries, shortcuts, file associations, etc.
The new BleachBit 0.2.0 cleans the .desktop files from the above examples. No, there is no promise your system will run much faster. And no, it doesn't clean everything yet---remember "Release early, release often"---but tomorrow's BleachBit will go even further.