With the news that United Airlines has given its stamp of approval to Uber as its ride sharing company of choice--without seeking input from the airports it serves--the question arises: How big and all-pervasive can Uber become?

Uber is already the most valuable startup in history, valued at $18 billion, fresh off investor rounds of more than $1 billion this summer. With such deep pockets, it's no wonder it has outsize aspirations, namely that it wants to partner with nearly any company and any app that could use its drivers. It's also spawning new services as fast it's minting new investment dollars, which could ultimately cause some headaches for the startup.

In August, Uber announced it would open up its application programming interface (API) to developers who want to integrate their apps with the service, and since then, more than 11 companies have reportedly signed up, including United, the hotel chain Hyatt, and restaurant app OpenTable. But Uber has also been on a new service tear itself, announcing this summer a grocery delivery option called Corner Store, which joins a same-day messenger service that it rolled out this spring.  

This Time's Different

If such a do-everything-for-everyone approach seems reminiscent of the 1990s overreach of now-defunct, consumer facing on-demand services too numerous to name, do not be alarmed, experts say. A great deal has changed since the dotcom bubble, with some caveats.

Namely, there's the mobile phone, which has allowed for a more "granular" experience for everyone involved, including the conveyance of near-real time information that allows customers to share their wishes with on-demand companies, and for companies to respond on the fly. What's more, smart phones have enabled such companies to mobilize ad hoc workforces that did not exist 15 years ago.

Another change, says Hrach Simonian, a principal at Canaan Partners in Menlo Park, California, is the relatively light infrastructure that such companies have today versus years ago. 

"The overhead and capital expenditure, and the workforce being variable to match supply with the demand makes services possible now that were not possible before," Simonian says.

Canaan has provided multi-million dollar investment rounds in on-demand services including dry-cleaning service app Washio, and the grocery app Instacart, which uses personal shoppers to gather items at customers' favorite grocery stores for delivery within an hour. 

The Challenges Ahead

The issue that Uber has to confront as it partners with more and more companies, and particularly as it launches services that are more tangential to driving--such as grocery deliveries--is to make sure its customer service is flawless.

"You have to go deep into the logistics to make sure every customer experience is great," says Ross Fubini,  a partner at Canaan says.

With that in mind, so-called vertically integrated businesses are likely to have a better chance, says Simonian. Uber excels at providing transportation services, but mobilizing a fleet of workers to choose groceries or deliver packages isn't part of its core business, and that could create problems.

And as companies such as Amazon, Google, and Uber move into same-day delivery services for things like groceries and other items, the question remains whether that can be sustainable.

"[In the past] on-demand businesses were spending money to acquire customers without a viable business model, and that's very different now," Simonian says.