Let me know if you have anything as a collateral except domain names. I can lend you 1.5 BTC
If the person who is selling domains is not willing to accept the domains as collateral then it should be safe to say that the domains being offered are not worth 1.5 BTC : D
Normally domain is not legit collateral and cannot be liquidated easily. And the value is varying a lot and difficulty to estimate. So most of the lenders wouldn't accept domain as collateral.
I would accept TLD's (never got an offer tough)... Not these ones tough, and only IF google analytics is properly installed and i get a full insight + raw server logs + proof of income from that domain...
Taking a domain as collateral is a lot harder than taking a lot of other stuff... It requires the lender to properly estimating how much the domain is worth... This means analyzing everything: the domain itself, the age, the past websites that used this tld, the present site, PR, alexa ratings, income, SE traffic, link partners,...
Next to that, there is a technical aspect: the domain should be moved from the person taking a loan to the account (and name) of the lender... A process that takes a lot longer than just locking a bitcointalk account... An escrow is also possible, but you need an escrow that has enough knowlegde about domain transfers and stuff...
Nevertheless, i think a domain CAN be good collateral, but only quality domain and only for really big loans tough, because it would be to much of a hassle for a .5 loan...
Imagine somebody would offer porn.com [NSFW] as a collateral for a 50
BTC loan... You would be a fool not to take it