I installed it on a netbook yesterday [using Opera, so the web installer was the way to go] and to me it's a case of technology running rampant - it updated after installation, downloading 127 MB[?!], the folder size swelling to 380 MB!
According to BD support, the main difference between the extension and the full install is that the full version will scan the HTTP traffic with both Antiphishing & Malware engines [locally stored signatures explain the monstrous download], as well as cloud detection; the add-on will only utilize cloud detection and Antiphishing -
Link
Also, BD admit that their cloud services aren't as large as some others, so they're relying a lot on HTTP scanning to cover for this at the moment -
Link
In version 1.5.0.201 they list 4 components:
- Add Filter
- Advanced Phishing Filter
- Malware Filter
- Search Results Analyzer [SRA]
It seems that there are a few other place holders in the add-on, such as "AntiFraud Filter", so obviously there will be more to come.
Strangely enough, clicking on the "Add Blocker" icon [feature not implemented yet] turns TrafficLight OFF. The search results are displayed almost instantly, but the analyzer takes long time to verify links/scan pages. Slows browsing down noticeably on this entry level configuration [single-core Intel Atom N455]. Turning it off... soon.