I don't think that people should shuffle 10+ times every time that they shuffle but when you build your deck if you want to randomize it you should shuffle that many times and if you don't want to play against a player that has mana weaved their deck it is a good idea to be thorough when you shuffle their deck. A randomized deck will perform, on average, worse than a mana weaved deck.
I agree that this is the best method we have for mixing our decks. My point is that it is not randomized after 7 really good riffle shuffles. 10+ has a better chance of doing a good job so if your opponent shuffles 7 times it is a good idea to shuffle his deck another 7 times to approach a randomized deck. Most people, myself included, are probably not good enough at shuffling to mix a deck enough to randomize it with the minimum number of shuffles. I don't think that people are trying to cheat but playing with physical cards is different than playing MTGO because MTGO is truely randomized and most games of physical magic are not. To improve my mtg skill I want to play games with randomized decks so that my choices in deck building (numbers of lands, balance of spells to creatures) can be made with better information. If other people want to achieve more randomness in their decks I think they should know that they should be shuffling more than 7 times.
It is commonly believed that 7 riffle shuffles are sufficient to randomize a deck based on a journal article published in 1992. However a more recent journal article explores the issue in more depth. Two quotes from the article are "The following two games use rising sequences to take advantage of how the GSR- shuffle is defined. They expose a lack of true randomness created by seven riffle shuffles." and "A computer program was written, which selected the most likely card to be at the top after a number of riffle shuffles. The results for the probability of success are displayed in the following table, where k is the number of riffle shuffles and m the number of guesses allowed to the computer. Given 26 guesses for a deck shuffled 8 times, the program succeeded 54.8% of the time. If the deck were truly random, then the success rate should be 50%." The program guessed correctly 59.6% of the time after 7 shuffles and 51.3% after 10 riffle shuffles. I don't know how to paste the table here so the full article is http://math.uchicago.edu/~may/REU2013/REUPapers/Guo.pdf
Keep in mind that this research was for a 52 card deck so a 60 card deck would be less randomized by 7 riffle shuffles than this research indicates.
Keep in mind that this research was for a 52 card deck so a 60 card deck would be less randomized by 7 riffle shuffles than this research indicates.