This recent Marketing Sherpa chart got my hackles up because it reminded me of so many conversations with newbie etail and ebusiness folks who ask "what should my ideal conversion rate be"?
Jen Doyle's post alludes to the fact that conversion rates are so site specific and 'user defined'...
The main issue isn't comparing conversion rates with other sites but:
Having proper site specific unique conversion events defined,Measured and in a
State of continuous improvement FOR YOUR SITE and business!
Your ideal conversion rate should be something better than your current rate, but isn't really productive to spend much time comparing it to others...
Whew. Had to get that off my chest.
"In analytics, a conversion event is what is known as a user-defined event. In other words, it can be anything you want it to be."
- MarketingSherpa: New Chart: How Do Your Search Conversion Rates Compare? (view on Google Sidewiki)