The criminal underground is populated with forum marketplaces where, allegedly, cybercriminals share and trade knowledge, skills, and cybercrime products. However, it is still unclear whether all marketplaces matter the same in the overall threat landscape. To effectively support trade and avoid degenerating into scams-for-scammers places, underground markets must address fundamental economic problems (such as moral hazard, adverse selection) that enable the exchange of actual technology and cybercrime products (as opposed to repackaged malware or years-old password databases). From the relevant literature and manual investigation, we identify several mechanisms that marketplaces implement to mitigate these problems, and we condense them into a market evaluation framework based on the Business Model Canvas. We use this framework to evaluate which mechanisms `successful' marketplaces have in place, and whether these differ from those employed by `unsuccessful' marketplaces. We test the framework on 23 underground forum markets by searching 836 aliases of indicted cybercriminals to identify `successful' marketplaces. We find evidence that marketplaces whose administrators are impartial in trade, verify their sellers, and have the right economic incentives to keep the market functional are more likely to be credible sources of threat.