Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of T-Mobile (TMUS 1.19%) held on to a gain of over 6% in afternoon trading after rising 10% shortly after Wednesday's closing bell. Investors are optimistic about the company's impressive subscriber growth, and also appear to be reacting to news that rival mobile carrier Sprint (S) might be preparing a buyout bid for T-Mobile.

So what: T-Mobile added 2.4 million new subscribers in its first quarter, bringing the company's subscriber count up to 49.1 million. This was the fourth consecutive quarter in which T-Mobile gained more than 1 million new subscribers. However, barely more than half -- 1.3 million -- of those new subscribers have an ongoing monthly plan. Investors were willing to overlook the steep losses T-Mobile is piling up to gain these subscribers; the company recorded a loss of $151 million for the quarter, compared to a $20 million loss in the preceding quarter, despite improving its top line by 47% year over year to $6.9 billion. T-Mobile's quarterly average revenue per user also slipped 8% year over year to $50.01.

Now what: "Users at any cost" is a strategy that has undone many companies, but investors are either willing to overlook it today or have instead decided to focus their optimism on a potential tie-up with Sprint. These two telecoms continue to lag far behind the big two, and consolidation might be the only way for them to compete over the long term. T-Mobile CEO John Legere pointed out during the company's earnings call that "at some point, in terms of the industry, it's a consolidation game," lending more credence to the rumors that Sprint and T-Mobile will come together in the future. However, T-Mobile's shares have nearly doubled in the past year, and its upside -- even when combined with Sprint -- may be somewhat limited given that the company has no dividend and no clear strategy for a return to strong profitability.