till today I really liked the widget on the sidebar. I thought it was an excellent piece of work significantly increasing traffic in my site. I absolutely agree to what you mention above with the loading time and partly visibility - “accessibility”

However we need to also mention that:
1) Tabbed content is very very popular and very convenient

2) Having the list of the popular POSTS on the rightside as I noticed from day one I installed the widget, draw users’ attention and they clicked on them. NOW in order to see this they first have to click on the “you might like these” adding an extra step to the process. An extra click is very important.

Placing the widget at the footer might look or sound good, but I guess Liveflows is not the only widget or content item that would like to have such a prominent place in a blog or generally USER SCREEN. Thus, as soon as another widget appears or in the case that other widgets function similarly, users will have to choose which one to place there.

Last but not least…. to me it seems like another toolbar (googlebar, yahoo and so on). Even though it is somehow discreet it still looks like a toolbar!

SUGGESTION: I REALLY REALLY like your work and I suggested it to other bloggers as well. What you can do is to simply allow the user to choose where they want the widget placed!!

Sidebar or footer? Simple as that!