Conventional wisdom says there's a tenuous relationship between eBay Inc. (NASDAQ: EBAY) and Google Inc. (NASDAQ: GOOG). Common knowledge says that eBay and Google compete in the realm of online payment services. It also seems to be an accepted fact that you can't use Google Checkout for purchases made on eBay, but did you know that Google Checkout has a back door into the eBay family? That's right, the eBay companies are not PayPal exclusive after all.

ProStores is an eBay merchants' option for the serious online retailer. ProStores is in fact an eBay company. ProStores directly competes with the in-house eBay Stores feature. The most interesting part is that ProStores allows the use of Google Checkout, while eBay itself does not.

Perhaps this isn't big news in the investment world, but I'll guarantee you that it's not common knowledge among eBay sellers, especially those who are straining to successfully operate eBay stores. The questions are, why does eBay keep this fact so quiet and why the double standard?

Could it be that eBay is using the availability of Google Checkout for ProStores as a marketing tool to create appeal to sign up for the ProStores service? If that's the case, then eBay is making a very odd, confusing, yet powerful statement. The availability of Google Checkout in ProStores says that eBay recognizes that service as a desirable option, yet the fact that Google Checkout is still being stonewalled from the eBay site itself says that eBay management still recognizes it as a considerable threat.

In the face of impending PayPal fee increases, which indicates that eBay profits are becoming stressed, the above scenario places some interesting angles on an already muddled eBay future.

What's it gonna be eBay: Do you Google or not?