Yeah absolutely - if you can get people to use them then I don't see anything wrong with them at all. You're not sneaking links into them and people are using them of their own accord, so nothing wrong with having them on the site for people to take and use if they want them.

I think the harder part will be getting people to actually engage with them, unless you're offering a superb platform or service.

Bear in mind any link you get will likely be an image link, so be sure to place your brand name in the alt text, and offer users a html snippet for placing on their site. If you start placing exact match anchor text in the alt text though and they do get heavily picked up, then there will be no variation and you'll likely pick up a penalty, so best to go with your brand name.

I seriously doubt links opening in a new tab would affect your rankings or cause any kind of Google penalty. Not something I think you need to worry about : )

Yeah absolutely - if you can get people to use them then I don't see anything wrong with them at all. You're not sneaking links into them and people are using them of their own accord, so nothing wrong with having them on the site for people to take and use if they want them.

I think the harder part will be getting people to actually engage with them, unless you're offering a superb platform or service.

Bear in mind any link you get will likely be an image link, so be sure to place your brand name in the alt text, and offer users a html snippet for placing on their site. If you start placing exact match anchor text in the alt text though and they do get heavily picked up, then there will be no variation and you'll likely pick up a penalty, so best to go with your brand name.