Google Catalogs is online once again, but has anything really changed other than the color from red to green? They have basically taken a cookie cutter copy of Google Book Search and made it search catalogs too. See this side by side comparison as we look for a "sweater" using both services.
Not only is it similar to Google Book Search, a speculative link can be drawn to Froogle -- a service that gives online and local merchants the ability to upload (and make searchable) their product lists. Integrating Catalogs and Froogle seems like a natural progression.
With all the valuable information stored in catalogs, why wouldn't Google link them with Froogle? It's a shame that the majority of mail order companies cannot make use of Froogle, when doing so could help both shoppers and merchants get what they are looking for.
On a product compatibility level it definitely makes sense, but now even the colors are right — both green.