Web Science/Part2: Emerging Web Properties/Web Search Ecosystem/Understanding the problems with Web SPAM/quiz

{Which of the following might be the reason for people to creating a link farm or link SPAM? + Manipulation of the ranking algorithms and driving relevance to certain landing pages. - Increasing the conversion rate of an internet service. + Increasing the organic search traffic a certain target site is receiving. - Increasing the paid search traffic a certain target site is receiving.
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{Why is link SPAM harmful to the business model of search engines? - It is not harmful to the business model of search engines. since there is no connection to advertisement revenue. + The search index is growing and containing useless information (rising costs) + The computation time of pagerank will rise (rising costs) - IF SPAM is not detected displaying search results will cost more time lowering the user experience of the search engine. + The promise of the search engine is that it will bring the user to the most relevant content and SPAM does not make the content more relevant. (lower product quality)
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{Why is it hard to detect link spam? + similar to click fraud it is even for a human hard to decide what the Intentions of a person putting one or more links was. + detecting certain patterns in graphs which are typically followed by a link farm is an NP-complete problem. - because spammers use bot nets and crowed sourcing to place links on blogs and wikis. - The entire link farm is usually placed on one domain and it cannot be said what the intentions of the domain owner are.
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