spamming your own clients very sad .
owe well good luck
I'm not sure why you think these subscribers are "your clients".
Take this example:
Let's say you have a site that sells health insurance in the UK.
You have a segment of 5 million visitors a year that:
* Only visit your homepage, agree to notifications, and then leave.
* Are from non-UK countries.
* Most probably arrived at your site by mistake, thinking your service applied to their home country.
* Have never returned to your site after their first visit.
That means you've got a group of 5 million subscribers annually who will almost certainly never be your customer.
The value of those subs in terms of push notifications is likely many thousands of dollars per year. Even with a 5% drop-off/unsubscribe per notification sent, you will quickly make-up those lost subscribers with new, similar subscribers.
Should you use push advertising?
I'd say yes. To each his own.
(This is just one example. There are thousands of similar situations).