Now this part I agree with. With all these hacks going on and risks of 51% attacks is it worth holding coins on exchanges because of the high risks? I would say do not take risks.
As long as it takes syncing blockchains and as much space as it occupies on your hard drive it might be better to keep your most valuable coins away from exchanges, for now at least.
The only reason to have funds on an exchange is to trade. If you finish trading - remove the funds.
Also check the withdrawal fees before depositing. Some exchanges have horrendous withdrawal fees.
Sometimes it is even worthwhile to exchange your BTC or coins to something like Doge to avoid paying excessive withdrawal fees. I often used Doge for sending between exchanges. The exchange rate is reasonably stable and the withdrawal fee usually quite low. Most exchanges have a Doge market.
Yes what you say is true but people (investors) are creatures of comfort and they often get complacent. After trading plenty of users leave their funds on the exchange rather then move them off the exchange.
As you said even a simple thing like changing BTC to LTC or another coin such as DOGE to avoid withdrawal fees is something that people do not really think about.
Regardless, the moral of the story is not to leave coins on exchanges, coins should be sent there to trade or to cash in and withdraw FIAT to bank.
Exactly what Tradesatoshi is playing at with regards to freezing accounts is highly questionable for some and highly obvious for others. Very soon they will be another collapsed failed exchange.