Doesn't surprise me - they refuse you for a visa if they have any suspicion that you're trying to immigrate. One time I was entering London and the customs guy was in a bad mood and decided to grill me. I made the mistake of saying I had a girlfriend in London that I was seeing as part of the trip - after that I got extensive questioning. Guy was halfway in a bad mood, but halfway having a girlfriend might be reason to immigrate in his eyes.

Nowdays regardless of what I'm doing, I won't say anything that'd remotely indicate that I might ever want to live in any country I'm visiting, lest I get in more questioning and hassle. And I'm an American, mind you, not exactly the country that people get the most skeptical screening process from.

If I was from a Baltic country or developing country, I'd try to casually work into conversation that I had serious commitments back home - good job, mortgage, graduate studies, serious relationship, things like that. (Actually, now that I think about it, that's what finally got me through that London questioning - when I mentioned I had to be back in Boston for my studies starting in late August, it was around July at the time IIRC, roughly five years ago)

With tourist visas you need to demonstrate non-immigrant intent. If the immigration officer was aware that your friend was actively applying for a greencard (ie, they're intending to move to the US), they'd have to go to extra lengths to show that they fully intended to leave whilst on that tourist visa (ie, they're planning on visiting the US).

http://en.wikipedia.org/wiki/Dual_intent

I know loads of people who have applied for the Greencard Lottery (a couple won Greencards) and none of them have ever had a problem getting into the US. I'd suggest the immigration service had other issues with your friend.

On the Visa Waiver there is (used?) to be a box to tick if you had been denied a visa. I would imagine being denied a visa and not winning a Greencard are two quite different things.

The greencard system is a mess in this regards. I'm surprised your friend actually tried to travel to the US since one of the first things they tell you once you've started the application is not to travel to the US until you have your greencard.

It's some sort of twisted logic where ICE thinks that you'll try to jump the line if you travel to the US on a non-immigrant visa.

This has simply not been true for me. I participated in DV lottery for quite a few years, and later on had multiple visits to US Embassy and never have had any kind of problems with getting my visas approved whatsoever.

I think your friend might be having some other issues, not the DV lottery.

Is there more evidence to it than one case? My parents applied for the lottery and had no problems getting tourist visas afterwards even though we have a lot of relatives living there. And Google does not seem to know about this problem either.