There are 2 different forms of digital marketing, each of which has its pros and cons.

Pull
Pull digital marketing technologies involve the user having to seek out and directly select (or pull) the content, often via web search. Web site/blogs and streaming media (audio and video) are good examples of this. In each of these examples, users have a specific link (URL) to view the content.
Pros:
Since requests are inherently opt-in, the size of content is generally unlimited.
No advanced technology required to send static content, only to store/display it.
Cons:
Considerable marketing effort required for users to find the message/content.
Some types of marketing content may be blocked in mixed content scenarios (i.e.: Flash blockers)


Push
Push digital marketing technologies involve both the marketer (creator of the message) as well as the recipients (the user). Email, SMS, RSS are examples of push digital marketing. In each of these examples, the marketer has to send (push) the messages to the users (subscribers) in order for the message to be received. In the case of RSS, content is actually pulled on a periodic basis (polling), thus simulating a push.
Pros:
Faster delivery - push technologies can deliver content immediately as it becomes available.
Consistent delivery - some push platforms have single content types, making it difficult for the user to block content by type.
Better targeting - since push technology usually justifies subscription, more specific marketing data may be collected during registration, which allows for better targeting and more personalization.
Better data - marketing data can be correlated to each request for content, allowing marketers to see information such as user name as well as demographic and psychographic data.
Cons:
Smaller audience - push technology not implemented on common platforms generally need client and/or server software before content can be created, distributed, and/or viewed.
Higher cost - less popular platforms may have higher implementation costs.
Lesser discoverability - smaller audiences mean fewer views mean less visibility in search engines.