本研究以2009年8月的莫拉克風災中出現的網路災情資訊平台及其行動者為研究對象。探討資訊平台作為民間災難資訊的彙整和即時傳遞，其能夠有效的條件為何？過去災難資訊與網際網路的研究主要探討，其作為新的媒體的傳播特質，因此，本研究除了建立在對資訊平台行動者擁有的技術條件之探究外，主要從「網路動員」的集體行動角度切入，探討該行動是基於何種人際網絡樣貌，而能讓此網路動員得以發生？ 透過次級資料收集和對資訊平台行動者的田野深度訪談發現，災情資訊平台有效性的問題不只是討論行動者擁有社會條件為何，更有趣的是行動者如何從中衍生有效性論述，並建構一套擬似「客觀」有效性標準，作為區隔他者資訊平台進而確立自身正當性的說法。借用Bourdieu象徵鬥爭(symbolic struggle)的分析觀點，對行動者如何進行資訊平台有效性的論述進一步分析。從行動者的有效性論述邏輯中，浮現一個爭奪資訊平台正當性的意見場域。災難情境作為一個突發性的例外狀態，不在政府例行化運作機制可以反應的程度，也因此使其原本作為救災以及災情資訊掌握的正統角色有了被挑戰的機會，而民間災情平台的集體行動則是挑戰此正當性的「異端」，透過網路開放式和平權化的特性，因而得以作到社會性的災情通報、彙整和溝通傳遞的資訊系統。 資訊平台的行動者作為一種網路動員並非僅是匿名而隨機的網友匯集，核心行動者多是屬於網路資訊圈或自由軟體的社群，其共享某些知識、價值或文化氛圍。他們熟悉網路資訊的傳遞或各種網站架構技術，再加上日常以網路資訊為共同興趣的聚會或交流形成不同的社群圈以及相對情感關係更緊密的「小圈圈」。線上、離線社交互動是跨越時、空限制的延續，彼此熟悉的程度高、信任度也高，也因此能協力完成高度動態分工的災情平台架構和維持。其他透過間接關係從網路上召募而來的資訊志工，則是受到災難感的情境影響，較平時更有機會產生對於組織或運作機制的系統信任。而災情資訊平台的有效性，除了建立在在網際網路技術物的開放和平權特性條件外，同時也在於行動者建構有效性論述，讓網路動員持續具有正當性，在災難情境中召喚更多人投入，形成另一股相對於「失靈」政府的公民動員的力量。 / This study aims at discussing the factors of information effectiveness presented in several online platforms built for Typhoon Morakot when it attacked Taiwan. Previous researches which have discussed information flows on the Internet during or after disasters focused on the media effect of the Internet. However, online information platforms built for Typhoon Morakot disaster were not only about the internet technology, but presented a social phenomenon of online mobilization. Based on this observation, this study underlines the discourse and relationship of the key actors ─ the bloggers and engineers, who constructed 4 major information platforms, and explored how these social factors make information platforms possible and effective. The methods of this research are through interview and second-hand data collection, and two results are analyzed and concluded as key factors which contribute to the effectiveness of information platforms. First, not only the actors’ technology or media background play an important role in effective problem of information platform but also their discourses about information effectiveness, which were based on their social conditions, were crucial. The key actors constructed seemingly “objective” standard in their discourse to justify their platforms’ legitimacy for distinguishing theirs from others. Borrowing Bourdieu’s theoretical lens of Symbolic Struggle, this study analyzed the context of actor’s discourses and found different logics of information effectiveness which emerged a field of opinion of discourse for legitimacy completion; at the same time, the government’s failure in dealing with the disasters as the background of the information platform’s appearing is also closely connected to legitimacy competition. The catastrophe that Typhoon Morakot brought to Taiwan was far beyond the government’s routinely mechanism can response to, and challenged government as the only orthodoxy of disaster information and rescue. Hence, civic action mobilized in delivering disaster information on several important internet platforms was the heterodoxy to challenge orthodoxy’s legitimacy. All these mobilization and competition of discourse are possible because of the open and equal-right characters of the Internet. Second, the online mobilization of information platform was not based on people’s random gathering, but based on most of the key actors belong to specific “circles”, such as those from the internet information or open-source communities. In the communities, these people are all interested in internet-related topics and are familiar with online communication technology. Moreover, they became much closer circles by regular meeting and daily communicating on social media and off-line parties for their common interest: internet and information. Their bonds and relationships are formed by intensive on-line and off-line daily practices which brought mutual understanding and trust ─ that is why they could work together and cooperate to keep the platform working.