Why .tel?
1 - A .tel plays a fundamentally different role than a traditional .com,.net,..., has very specific and unique content, and is published in a different format and medium (DNS instead of Web). Therefore, Google and other search engines will want to index .tel content in addition to .com content, and will not penalize a company for having both a .com and a .tel, as opposed to those that multiply websites under .com, .biz, .co.uk, etc... This will give companies double presence, with both a .com and a .tel.
2 - The .tel data is fully structured, and therefore very easily readable and understandable by search engine crawlers, as opposed to standard web page content that needs advanced parsing algorithms that often misunderstand the content (reading a fax number as a main number, for example).
3 - .tel communications content is very easy to maintain, and can be updated at significantly shorter intervals than .com informational content. This gives search engines more incentive to re-index .tel content at shorter intervals as well.
4 - Local search engines will index by preference .tel data thanks to .tel's focus on communications and location information.
5 - Finally, .tel has the best ROI in the SEO/SEM business, being extremely cheap ($15-$20/year) given all the features above.