First of all it is not necessary that Most popular or Most voted ideas should get Implemented by the Ubuntu Developers team.

I mean if anyone is so Inclined towards bringing it in Ubuntu , then there exists other way using Launchpad PPA where you can Build your Idea and Implement in more Customizable form.

From Ubuntu brainstorm Wiki page

Ubuntu brainstorm provides a simple way for anyone to contribute ideas
for improving Ubuntu. Ideas are voted on by the user community and the
most popular ideas are brought to the attention of the development
teams

From idea to feature

There are several routes from idea to implementation:

• The idea submitter implements by themself, and contributes the package or patch to Ubuntu.


• The idea generates interest, and several volunteers form a new project to blueprint and implement the idea.


• The idea attracts interest from the appropriate Ubuntu Teams, which form a working group or schedule a UDS Session to blueprint and milestone the idea.


• The idea concept influences another forum, and is implemented by an unrelated group.

Ubuntu blueprints

For complex changes, write a 'blueprint' based on the result of the Brainstorm idea.

• A blueprint is a feature design document. It is used to describe a proposed feature in enough detail for a developer to implement it (not quite the same as a specification, though that term is often used).


• Anyone can start a blueprint though some software design or
  development experience would be useful. After a first draft has been
  composed the blueprint is typically discussed on an appropriate team
  or project mailing list, forum thread, or at a development meeting
  like UDS.

For example Here are the ideas about Ubuntu that are currently being implemented for the Ubuntu 12.10 Quantal Quetzal release.

From my point of View,

Brainstorm is Platform to improve and contribute in innovative way to Ubuntu which includes bringing attention of Developers Team towards your Idea .

Alternatively bringing other proposed ideas or own ideas to life by developing and implementing it using PPA, if it found more useful then it may get ended up in Official Ubuntu Repositories bringing more interested Developers and volunteers to develop and maintain it.