If you include all the addresses I had on various exchanges, I have probably used at least 250-300.
Well I didn't count my addresses on exchange sites because I don't consider them part of my wallet.
I suppose that's true since the address might be yours, but the wallet still belongs to the exchange. I would still technically consider them as my BTC addresses. Without them I would say I used roughly 100+ addresses.
You've got that right. It could be considered your address in exchange's wallet.
No matter how much security an exchange offers, it always makes me uneasy keeping my coins there for an extended period of time. Nothing beats having your own wallet.
I used to think that too. That is, until I entered the world of altcoin trading. Compared to setting up wallets, it is so much more convenient to just have the coins sitting there on an exchange. Especially if you are a speculator. I know it's not good security-wise, but I can understand why exchanges are such a popular place to store one's own coins.