Are email lists a good way of building up your business?
If you scatter gun 100,000 people with unsolicited emails you will probably create a negative image for your business - bought email lists are not as effective as somebody saying "I'm interested in your product". Have a look in your own inbox for proof this approach does not work. Do you deal with the unsolicited direct (spamming) marketers and do you trust them? Do you read all the junk mail that drops onto your doormat? If you send out of 10.000 emails you might get a response from less than 1% of them - there is a possibility you might not get any quality leads at all.
Companies that attempt to generate sales entirely through indiscriminate direct mail, cold calling or email campaigns are going to find the going tough. Unique leads for your niche market are the best leads and by targeting the people who really need your product you stand a better chance of getting the positive response you require.