I think the answer for most ethical question relates on how the user will feel in the end with some limitations. For example, if you are going to a private party and you are telling people that you throw better parties, cheaper prices and more fun…and you also give them a flyer or something. It may sound like you are spamming the “hard earned” customers of the one that throw that party. If they go to your party and they are having more fun and they come to you thanking you for telling them about it how would you feel?
Spamming is sending something to someone who didn’t asked for it, however, if the user finds is valuable is debatable if is spam or not since you are giving value and perceived as something valuable. The problem is that do you know how much value are you sending? For the ones that doesn’t find it valuable it may be perceived as spam.
After going to lots of Startup meetups, I found that most guys in the startup communities are or want to look like “extremely ethical”, especially the founders from the tech side. Those guys even think that sales guys are some kind of spammers(some of them really are), but if you are bringing everything down rationally, spamming can be even the ads on a website or TV since I’m not asking for them.
I also found that marketing guys are more “open” or “ballsy” at promoting products than tech guys. That’s why it’s good to have a co-founder with marketing/sales experience, being too ethical when you shouldn’t it will hurt you more than help. If I’m going to the bordeline actions side, I don’t think there are any successful startups which haven’t done something borderline, they are just better at hiding it.
Anyway, asking a question like this on a public startups forum most of the answers would be to not do it, if you ask on a marketing/sales forum most of them would say it’s ok if you do it moderately/don’t cross the line. A lot of these ethical stuff has a lot to do on how you’ll feel rather than if it’s spamming or not since spamming can be subjective. I think for most people, sales calls are spamming( I’m really pissed off when someone is calling and trying to sell me through the phone some crap) but it doesn’t mean that it stops them… so many companies do it anyway.
Do what makes you feel the best.