I'm not a big SL user, my capped satellite broadband just won't allow for more than a few hours a week. With that said, one thought that crossed my mind is the possibility of a market index for SL's economy.
Chatting with Olasofia last night about the subject brought out some initial thoughts regarding such a market index of goods and services. Since there is already an economy in SL, an index may have some economic and trust effects. There is already an index of Linden $ exchange rates, mapping $/L$/goods/services may be interesting.
The mention of L$6000 stiletto boots vs. L$1 for a complete outfit came up, getting the later to "fit" to one's avatar vs. possible custom fitting for the former. Automating the process of finding the price for every thing/service on SL may be the show-stopper for this whole idea.
Adding a vote component for each and every content creator and service provider would add a measurement of "trust" to the SL economy, although separating content creators and resellers would probably be another sticking point. Advertising and word-of-mouth currently builds legitimacy within SL, an index of trust or value could add extra value. I have seen voting mechanisms at various venues in SL, but I'm not sure what they are about. It would seem necessary to track visitors vs actual customers, but recording a vote for the satisfaction of the product/service purchased vs. the shopping experience could be another show-stopping difficulty.
In summary, the index I have in mind would contain all products and services on SL, who creates/provides each, their retail price, and a vote of satisfaction with each product/service. Unsure of many things, I wonder if Linden Labs provides facilities for obtaining such data. Mono may be able to deal with the data, if it is, but I'm fairly certain that this whole chain of thought will need to be reconciled by someone who is more clueful than I.