Twitter Marketing

Hi guys I was just wondering how effective you all find Twitter marketing, I have 3 main accounts totalling close to 20000 followers aged followers at that ie similar amount of followers for 6+ months, no matter how much I plug a product or site I get zero response, however I have 3 pages on Fb with similar figure and do actually gain some leverage... So is Twitter still or was it ever a good marketing platform, your thoughts and experience will be well received
Thanks

Sounds like you where blocked from the search results, that can happen if you use the same hash tag to much or have been reported as a spam account way to many times