I noticed you asked the same question on SU and got a similar comment to what @DA01 wrote. Both DA01 and Jaips are correct - you are using your tool improperly.
Save for Web & Devices means exactly that. It is for saving for web and mobile devices. The purpose of the
Save for Web dialog is to allow you to compare multiple ouputs side-by-side and choose the one with the best trade-off of image quality and file size. This is specifically geared for smaller images that needed to be loaded quickly on systems with limited bandwidth or resources. On no web page should you ever be displaying a 10mb image. Same goes for mobile phones of all calibers.
If you routinely load >10MB RAW images from your camera, you likely have a preference for how they should be saved. There is no format that you can access in
Save for Web that you can't also use in the standard
Save as... dialog - in fact, it has more options for you.
Save for Web only saves in GIF, PNG, JPG, or WBMP.
Save as has those formats and also has EPS, RAW, TIF, and a bunch of other formats.
All that aside, you could theoretically be using very large original files to produce web-ready images. If you're doing that, you're probably going to resize the photos once you get to the
Save for Web dialog. Instead of waiting for that stage, go ahead and resize prior to launching the dialog.
Heed the warning. Your tool is working properly.
If you're resizing your image, you likely also want to sharpen your newly resized result. Since
Save for Web doesn't allow any sort of post-resize filtering, you would not get the best results by using this tool for resizing. Maybe you should look into an action or batch script that will automate the process of getting images from your camera, resizing them, sharpening them, and saving them using a predetermined format.