Let's say that 10% (a small minority) of companies offering hosting adopt the same strategy, and that 20% (again a rather small minority) of them manage to get your email address (assuming that the other 80% missed your tweet or did not monitor specifically the twitter account or were lazy or are incompetent, it doesn't matter).
If there are 1,000 such companies, in no time after you post a tweet on your current hosting company you will find in your e-mail box 20 (unsolicited) messages, if there are 10,000 such companies that will be 200.
Would you react in the same manner?