edit: the notion of "existing accounts" is broken here; "new accounts" are free/cheap and not related to identities.
That's somewhat of a moronic statement considering the namecoin crew invented the idea of merged mining. But I digress...
I remember back when namecoin came out... they started the difficulty at 512 instead of 1 (bitcoin's initial difficulty) which made sense at the time, because GPUs were everywhere by then. But with namecoin being so new (and worthless) the difficulty soon dropped to the ~200 range, and anybody with a few GPUs could literally mine 1,000s of NMC per day.
Case in point, the 50 NMC they charged for the first domains was still much too cheap. One could theoretically mine with an average rig for 1 week and register a few hundred of the first domains available.
One way you could hinder them is geometrically increasing cost of registering additional domains from existing accounts.
Examples:
- Adam wants to set up his personal site. It costs him X to register.
- Bob wants to set up his personal site, and 3 hobby sites. It costs him X + 2X + 4X + 8X = 15X or (2^4 - 1)X.
- Carl the domain squatter wants to register 100 domains. It costs him (2^100 - 1)X. This could be defeated by changing Carl's business name, or other details, which creates extra hassles for him.
Edit: Didn't know that registering new accounts is near 0 effort. Guess that nixes this idea.