i think there are similar accusations against hitbtc and yobit too.
Hmmm, I'm not so sure about adding those columns, as almost no exchange is perfect. Scam accusations exist for almost every exchange out there. However, what do you say if I add a column of "frequency of accusations at Bitcointalk" and list the total number of accusations received by each of the exchanges within this forum till now?
it's a tricky issue but obviously some exchanges are more trustworthy than others. one metric could be trust flags on bitcointalk. for example, livecoin has a red trust flag with significant support: https://bitcointalk.org/index.php?action=trust;u=462136
but if an exchange is really small or doesn't have a big forum presence, they won't necessarily be flagged. the complaints against tradesatoshi are mounting. coinmarketcap has also begun warning about tradesatoshi: https://coinmarketcap.com/exchanges/trade-satoshi/
at some point, one should stop recommending these exchanges at all. if they stay on the list, there should be some indication of the issues.
i don't consider 20 minutes "slow-paying". i'm thinking more about withholding withdrawals for days, weeks, indefinitely---like mt gox and cryptsy were doing before they went down. keeping wallets in "maintenance" mode for weeks or months constitutes similar scam behavior. and i wouldn't have a separate column for slow-paying......just one column to cover all scam issues.