Life was so much easier when Twitter wasn't worried about making money. Some spectacular venture capital deals propelled the company's value to over $1 billion, and user trends shot bragging rights up proportionately. Its ascendancy resulted in large part from the efforts of the Twitter ecosystem where companies developed 70,000 applications that have made life easier or more measurable for Twitter users. It's easy to lose track of how much of our Twitter interaction lies on third-party apps – from photo sharing to smartphone applications to URL shortening.

As long as Twitter's functionality ambitions remained modest, the ecosystem knew it would thrive. As we head toward the Chirp conference for Twitter application developers concerns over the future of the ecosystem abound. Here are five reasons why the companies around Twitter may start to worry about the microblogging juggernaut.

Last year, Twitter said it had two goals for 2010: generate revenue and make acquisitions. At the time, the company was still sitting on a significant portion of its last round of capital, and given the $20 million annual burn rate revealed late last year -- plus the revenue it's generating -- it's unlikely that Twitter has had to deplete its coffers. So, Twitter has cash to put to work, and now we're seeing what that means.

On its blog, Twitter announced Friday that it has entered into an agreement with Atebits (aka Loren Brichter) to acquire Tweetie, which is one of the top Twitter clients for the Apple (AAPL) iPhone. In addition to acquiring the application, Twitter is also picking up talent. Brichter's efforts were good for a 2009 Apple Design Award, and he'll be part of future efforts to get Twitter for the iPad off the ground.

Michael Moe knows how to make headlines: Talk about Twitter and predictably people will bite (I'm proof of that). He led the team at NeXt Up Research that calculated the value of the micro blogging service and arrived at $526 million to $674 million -- half what Twitter is generally believed to be worth.

Really?

The team estimates that Twitter will generate revenues of $114 million to $134 million in 2013. In 2014, Twitter is expected to post revenues of $126 million to $148 million. This is far more conservative than the valuation implied by the company's most recent round of venture capital investment, which puts the company's worth at more than $1 billion.