Send a Thank You After Interviewing

There is really no  "downside" for sending a thank you note after a job interview, although most job candidates don't bother to do it. Sending a thank you --if done reasonably well-- will not hurt your chances at a job.

Worst case, your thank you will be ignored.

Best case, it will improve the impression you left after the interview, making you stand out from your competitors..

For a good discussion on 'Thank Yous'  see the article here