There are some things in educational measurement that are not debated. Foremost, the purpose of instruction is to improve learning. The purpose of assessment is to improve instruction, which in turn improves learning. In other words, it’s all about the learning—debate over.
Some researchers (myself included) have become sloppy with our language, labeling assessments "for learning" to be formative and assessments "of learning" to be summative. So, under this lax jargon, a multiple-choice quiz used by the teacher in the classroom at the end of instruction for the purpose of tailoring additional instruction would be deemed "formative." If you follow the rhetoric from national "experts," technical advisory committees, or other learned people, then I have just offended many!
Currently, there is much discussion regarding formative assessments and the need to balance the multitude of assessments that might be used during a school year. A good place to start might be with the paper by Perie, et. al. (2006) posted to the CCSSO SCASS website. You and I might not agree with the classifications or the terminology, but the classification scheme used by these authors helps to contextualize the debate quite well and may even allow you to make up your own mind.
What does, however, put peanut butter into my cognitive gears is all the arguments and wasted effort I hear regarding what exactly does or does not constitutes a "real" formative assessment. I even heard one nationally recognized measurement expert comment that, by definition, no assessment constructed by anyone other than a teacher can be called a formative assessment. I try to remind myself (and others) that at the end of the day only one thing matters: What have you done to improve learning? I doubt that arguing about definitions of formative, benchmark, or interim assessments helps with this.