if you look at most product startup they all have started with shady growth tactics (stealing contacts or propagating trought fake invites to your contacts or pretending you to be on a network to lure your friends)

of course once they did it they where quick to plug the hole and denounce it as unhetical

spamming of course isn't a cost effective solution to reach people needing a product, but social network propagation trough referral still is highly effective

you can also buy targeted mailing addresses from selected companies, but the big, accurate lists are costly to come by - but those give you an incredibly focused group

> look at most product startup they all have started

Now, maybe, I don't know what you mean by "product startup", or even the word "most", but having burned a fair amount of shoe leather in my time, and having been associated with startups that have done nigh on a billion (USD) in sales by talking to customers, in their shops, and showing them goods, and signing contracts for delivery and SLAs, I surely would like you to back up this assertion.

I'm confused. Are you saying promotion == spam?

Posting your product indiscriminately, as is the premise of the OP, is spam.

Promoting your product via Twitter or your friends is fine. (promoting a submission on Hacker News [i.e. highlighting the submission itself in an attempt to vote manipulate] is against the site rules, which is not spam but still bad)

But it's not necessarily indiscriminate. Many of these are sites that want submissions. Even Hacker News is OK if you're doing something relevant to the audience.

As an example:

https://news.ycombinator.com/item?id=14202456

Edited my comment to clarify that voting manipulation is bad, not Show HN itself. Show HN of course is fine.

Getting exposure helps. How it's done is a different question. Posting your startup to directories/curated collections or blog is perfectly fine. Spam begins when it's unsolicited.