Social network advertising is currently one of the most effective advertising types available to promote a product or a brand. The problem discussed in this paper concerns the possibility to ensure that advertising reaches really interested users, and also to prove this. At this aim, we propose the use of Blockchain to store users' interest and to obtain an assertion that a user is interested in a product before the advertising is shown. The proposal has been implemented by a Solidity smart contract in Ethereum and has been shown to be effective and cheap.

In new generation social networks, we expect that the paradigm of Social Internetworking Systems (SISs, for short) will be more and more important. In this new scenario, the role of Social Network Analysis is of course still crucial but the preliminary step to do is designing a good way to crawl the underlying graph. While this aspect has been deeply investigated in the field of social networks, it is an open issue when moving towards SISs. Indeed, we cannot expect that a crawling strategy which is good for social networks, is still valid in a Social Internetworking Scenario, due to its specific topological features. In this paper, we first confirm the above claim and, then, define a new crawling strategy specifically conceived for SISs. Finally, we show that it fully overcomes the drawbacks of the state-of-the-art crawling strategies.