Does submitting my research to a GENDEX site increase the likelihood of others requesting information from me?
The bi-langual website FamilyTreeSeeker (StamboomZoeker in Dutch) is a website which indexes GENDEX files. The FAQ on this websites explains the GENDEX format (originally thought up by Gene Stark) - http://www.familytreeseeker.com/faq.php?l=en&p=14
The GENDEX file provides a means to index genealogical data published on the web. I do not think TinyTafels are a good alternative for this. The microdata scheme historical-data.org might be an alternative, this provides a mechanisme website owners can user to provide (invisible) information indicating what the genealogical info is, so search engine crawlers (like Googlebot) have a better understanding of the content of the page.
Another page in the FAQ lists the software programs capable of creating GENDEX files: http://www.familytreeseeker.com/faq.php?l=en&p=5 Although the big commercial players are not on this list, there are quit a few programs! Some "genealogical hosting providers" (like Genealogie Online) also provide indexes to FamilyTreeSeeker
Finally, to anwer the question: I think the more "findable" your data is, the more people discover your content and might provide feedback. The very easy step to submit a GENDEX file (index to your data) can help.
I have uploaded my base data as a GENDEX file for about 3 years to FamilyTreeSeeker. During that time, I have only had one request for information from that source, which proved profitable to both of us. As my main research is a locked private site, this visitor is unlikely to have come. With the minimal effort to upload, I consider this was worthwhile and suggest all could be helped by the small task.
As Andy says above, GENDEX sites are almost non-existent now. I don't know of one to even quote.
GENDEX stands for GENealogical inDEX. It is a file format for indexing Web pages containing details of persons. The supposed advantage would be that it matches on multiple criteria and so would find more accurate matches. For instance, full name, date & place of birth, and date & place of death.
In practice, though, these fields would never be matched verbatim so the effective accuracy then depends on how clever the algorithm is. Consider how a name may have different forms, different spellings, and may even change at certain points in someone's life. Dates may not be known precisely, and there's still no standard way of referencing a place.
I sympathise with the designers of that format since some genealogical sites do not put as much effort into the matching process. For example, genesreunited (run by brightsolid), which has a good working model for making comtact with distant relatives, returns so many matches - most of which have the flimsiest correspondence - that the feature loses its usefulness.
My answer, based on the fact that the format is no longer popular, would be 'no advantages'.