Yes, it does happen on some text inputs, it tends to depend on relative size (for example, I recall zoom in landscape but not necessarily in portrait, etc.).
Generally I welcome it, because I can click on the teeeny input field and have it come "closer" to me for editing then get out of the way.
I've always been a fan of moving mobile web towards the standards and behaviors of native apps which generally did not require zooming to get tasks done.