"To achieve the streamlined feel we were after … we had our own intuitions about what was and wasn't useful in current browsers, we had no idea how those ideas matched to reality. So in typical Google fashion, we turned to data; we ran long studies of the browsing habits of thousands of volunteers, compiled giant charts of what features people did and didn't use, argued over and incorporated that data into our designs and prototypes, ran experiments, watched how our test users reacted, listened to their feedback, and then repeated the cycle over and over and over again."
Many Tab OverflowWe don't have a complete system for handling many open tabs right now. We let tabs grow infinitely smaller. This ends up looking bad when there are a very large number of tabs open. We chose not to go with an overflow menu or scrolling tab strip like in some other browsers because we think there are other usability problems with those approaches. Specifically, when you implement an overflow solution you generally pick a minimum "readable" width for the tab and overflow tabs when there are too many at that width to fit. The problem is usually that that width seems to be too wide, so there can be unnecessary overflow in conditions where a smaller tab width would have meant all of the tabs would have fit. We also don't really like the drop-down menu approach as it has a spatial disconnect (vertical scanning vs. horizontal tabs) that makes it clumsy to use quickly. In the end, we would like a system that doesn't over-zealously clip tabs out of the tab strip so that people with many tabs can still access their tabs with one click.Disoriented Anchor TabsOpening tabs next to the tab that opened them can mean for some use cases that the behavior of having a few "anchor" tabs positioned at the left edge of the strip is more difficult since tabs opened from them are opened in between. We like the idea of "tab pinning" or "locking" as a solution for this, but haven't invested a lot of time in designing how this might work just yet. There may be some overlap with "startup tabs" in Options.Restoring Mistakenly Closed WindowsWe also don't prompt when you close a window with several tabs. The reason we don't do this is that one of our core design philosophies has been to avoid modal question prompts that interrupt the user when they're trying to get things done (in this case, use a standard window control to close the window). We're aware that the prompt has saved people (including ourselves!) using other browsers from losing tabs, but we have been trying to come up with a more creative system for helping this scenario that doesn't interfere with the window's close button. In recent trunk builds, you'll find that you can re-open a recently closed window from the New Tab Page, and that the "Recently Closed" section of the New Tab Page now spans multiple sessions. This is a good way to "undo" an accidentally closed window, in the same way you can "undo" an accidentally closed tab. To try this out you can get on the Google Chrome Dev Channel.