The existing realtime search players are putting on a brave face, however I expect they are quietly concerned. Google and Microsoft are big players and have a lot of resources at their disposal to provide a high quality realtime search offering that will displace the existing players.

Each realtime search engine has slightly different approaches, but at their core they rank the links that appear on twitter (and other link sharing sites) based on the number of "votes" for each link and then apply some other weighting metric(s). The early players have had good success in building highly relevent results, but you would expect Google and Bing to be more than capable of replicating this themselves.

Presumably the existing realtime search players have other strategies to protect themselves from this inevitable intrusion by Google and Microsoft. According to Chrunchbase, Topsy has raised $15m and Oneriot $30m, so I'm sure their investors would be concerned if their whole strategy is focused on being the world leader in realtime search.

I expect the next 6-12 months to become very interesting in the realtime search space as these existing players attempt to differentiate themselves and presumably carve out a niche.

My startup has two unique offerings to throw on the realtime search table. While I would love to spell these out and show the world, it will have to wait for the time being.