I've heard it said before... sock yarn doesn't count as stash. Sure, it's a cute thing to say, but I didn't see the reasoning until now.
Sock yarn is intended for socks. I know, that's obvious, but the statement has important ramifications. Yarn in any other weight doesn't have a set purpose. Lace weight could be used for a shawl, a scarf, a doily... Worsted can be bought in a small amount for a hat, or a larger amount for a sweater or afghan. If you find a fabulous DK (like I did recently: Rowan's Tapestry!) and you just go ahead and just buy some with nothing in specific in mind, you may not have the right amount when you choose a project. (Why I still haven't bought any Tapestry, yet.) You'll inevitably buy more than you think you'd actually use, because you don't want to come up short. A couple purchases like this and your yarn drawer turns into your yarn room... and a problem with over abundant stash. It's simply hard to know how much yarn to buy when you find something yummy, and it turns into stash.
Sock yarn, being intended for socks, is typically sold in amounts appropriate for a sock project. It is therefore easy to know how much you need. You can grab a skein and know that you'll pair it with a perfect pattern later and have the right amount. Sure, there are exceptions. Knee highs would require two skeins and mitts might need less. But, if you like knitting socks, the yarn is easy to just grab when something tickles your fancy and you don't have to feel any guilt about it spilling over out of the closet and all over your living room.
I like sock yarn for these reasons. And I can't wait to see the new skeins I just ordered that won't actually be stash. :)
