When I go to ThinkGeek I know that I'm being pandered to as a geek, but that's okay because ThinkGeek treats the geek demographic with respect.
It's all too easy to just slap some popular geek culture references on a t-shirt or a hoodie and call it a day. Likely profitable, too, considering how many "daily tee" companies I've seen. Those companies don't get much brand loyalty, they could disappear tomorrow and a replacement would step right in to fill the gap.
If anything happened to ThinkGeek, I don't know if anybody else could fill their shoes without years of effort. Whatever happens, I hope they retain their brand and their reputation.