I'm currently playing a bit with sRGB-corrected rendering. So I tried WGL_ARB_framebuffer_sRGB.
Rendering sRGB to the window framebuffer is intended, so I enable GL_FRAMEBUFFER_SRGB.

In a second step I do some offscreen-rendering into a GL_RGBA8 renderbuffer. For this step I do not want sRGB rendering and GL_FRAMEBUFFER_COLOR_ATTACHMENT_ENCODING is returning GL_LINEAR like expected.
So I assume, that even though GL_GFRAMEBUFFER_SRGB is enabled, sRGB has no effect when I render into this FBO. Unfortunately, despite GL_RGBA8, sRGB rendering is still being done and my readback-results get wrong.

Also, I noticed that glClearColor() is affected by sRGB rendering. Where in the ARB_framebuffer_sRGB specs is this effect hidden?
I only found this:
14) How is the constant blend color handled for sRGB framebuffers?
RESOLVED: The constant blend color is specified as four floating-point values. Given that the texture border color can be specified at such high precision, it is always treated as a linear RGBA value.
(Btw, the specs erroneously refer to the texture border color!)

So I assumed that glClear is probably not affected by sRGB rendering as well... Am I wrong?

I've tested this on a QuadroFX1700 (266.45), WinXP64