I have a crumb topping (margarine + brown sugar + flour) that I usually make double or triple the recipe of and then freeze. Sometimes I don't divide it evenly and end up with extra dough when I defrost a section. Can I refreeze the dough or should I just toss it because it'll affect the taste? (What about cookie dough?)
Generally, freezing and re-freezing is not a big issue. Some things just shouldn't be frozen (certain fruits and veg), because when frozen the water contained in the cell structure expands and in turn bursts the containing structure, which causes mushiness. Meats can be refrozen with a slight moisture loss. From what I was taught by my old pastry chef, this whole notion of freezing and refreezing being dangerous was started when electric freezers were just coming into the market (first half of the 20th century), and the cold storage and ice companies were scared of the potential loss of their business (which absolutely happened). It was them that advertised that this refreezing could be detrimental to health. Truth is, refreezing just sends the item into a (mostly) inert state, where bacteria can't harm the item by propagating. However, your question is about the taste and how refreezing pertains to cookie dough. It's not a matter of the refreezing that has an effect on the taste, rather how long things stay in your freezer. You can thaw, refreeze, thaw, refreeze as much as you want. Happens all the time in commercial kitchens and bakeries. The key is to not make so much that it stays in the freezer too long.
Here's and article I found, haven't looked for any others:
Freezing and re-freezing dry topping should be no problem at all.
Freezing disrupts the cell structure of things like meat, causing texture change. Repeated freezing/thawing will make this worse. There shouldn't be any effect on the taste, unless perhaps you're going to store it for some months whan you might get rancidity.
For foods suspectible to microbiological growth, there will be stages during the freezing/thawing processes where microbiological growth is possible, which will be repeated in every freeze/thawing cycle. I think this is the real reason for the official line that re-freezing is unacceptable.
Neither of these apply to dry crumb topping, but the microbiological aspects may be an issue for doughs containing water.