1. People use Poloniex because everyone else uses it. Most coins have 50%+ volume traded on poloniex.
2. Bittrex - no stupid limits, good volume, and trustworthy
3. A good community, and good support
4. An exchange is a great idea!
5. If you mine alt-coins yeah!
6. Nope! You can arbitrage and make money. Not just with BTC, but with alt-coins. If you can buy it for 0.01 on one exchange, and sell for 0.011 on another, do it! Sometimes whales who dump or buy big amounts create gaps - take advantage

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