I'm almost 40, so neither young or old. Short version: When I give gifts I just give them and don't expect anything in return, even gratitude.
Long version: I generally think it's in inappropriate to provide gifts to co-workers in the office. I'm in the minority on this probably, but it sets up a whole slew of minor and major problems, like where's my thank you?. I am working in a group now that provides small gifts at Xmas and after returning from exotic vacations. This is nice but makes me uncomfortable at times since I've only been at my new job 5 months. I'm also pretty much an atheist (I'm sure I'll get slammed for this), so Xmas isn't a big thing w/ me. That said, I don't stress about it that much, and I always say thank you.
Thank-you notes are sent sometimes to family/friends for other occasions. I'm actually big on mailing cards and all that, just not to co-workers unless they were throwing me a shower or another party of some sort.
I used to email thank-yous after job interviews. However, they made absolutely no difference on whether I got the job or not, and I just felt like I was clogging up their inboxes. Mailed thank-yous aren't quick enough. Nonetheless, after I got this last job, I did send a thorough email thanking my now boss for the opportunity. (Sidebar: I learned that I was the only interviewee to wear a suit. For a financial services firm!!)