The above solution does have a resource penalty, at least on my Windows XP.
It's not as efficient with your computer memory when compared to a Yahoo webmail interface that natively supports tabs.
Here is example resource usage:
Chrome with a single tab open to
Google
Chrome with a single tab open to mail.yahoo.com:
Chrome with many tabs open to Yahoo Mail due to opening many emails in separate tabs:
My primary computer is older but I have the max 4GB memory installed. Windows XP is able to use around 3.2 of the 4GB memory.
A computer with less memory could start to slow down if too many tabs are open in Chrome (or any other web browser)